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Lovatt, Peter (2002). The radio war waged by the Royal Air Force against Germany, 19401945. PhD thesis The Open University.
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ABSTRACT
This thesis explores the origins of the Radio War, which
started in 1940, and explains how the United Kingdom came to
fight a defensive campaign until 1942. In the first part of the
thesis the Luftwaffe use of beacons and beams for navigation
and bombing purposes is explored, together with the actions
taken by the Royal Air Force to frustrate the Luftwaffe from
using these aids and preventing the destruction of British cities
and industry, which clearly would have been totally disastrous.
The second part examines the reasons, which led the Royal Air
Force in 1942 to adopt a more offensive posture in order to
provide protection to allied bomber aircraft from the effect of the
greatly improved German radar-controlled defences.
The thesis justifies the creation of entirely new formations
to control the application of countermeasures and reveals how
the headquarters of the new formations were provided with the
latest German intelligence information, essential to their role.
The thesis goes on to investigate the critical part played by
British Research, with especial reference to the
Telecommunication Research Establishment. The thesis
demonstrates how the Royal Air Force was forced to create a
radio countermeasure organisation at a critical time in 1940, at
the beginning of the German bombing campaign against the
United Kingdom, how the application of these measures helped
to protect Royal Air Force bomber aircraft and later successfully
assisted in D-Day deception and radio countermeasure plans.


THE RADIO WAR
WAGED BY THE
ROYAL AIR FORCE
AGAINST
GERMANY,
1940 - 1945


SUBMISSION DETAILS
THE RADIO WAR WAGED BY THE ROYAL AIR FORCE AGAINST GERMANY 1940-1945
Peter Lovatt, BA MCMI
PhD
Department of History
Date of Submission – 15 November 2002
Name of Sponsor and Collaborating Establishment - None


i
ACKNOWLEDGMENTS
One morning, over fifty years ago, I was sitting in the
Intelligence Room at RAF Oulton, reading the after-raid reports
from the previous night's operations, little realising that one day
I should be in a position to write about the highly secret
activities in which I was involved. In researching and writing
this thesis I have been fortunate in the help and support I have
received from my Supervisor, Professor Arthur Marwick.
Without his advice, expertise and, above all, encouragement, it
would not have been written. I should like to thank Dr Annika
Mombauer for her suggestions and assistance and also Dr
Christina Goulter for her helpful comments. I owe a debt of
gratitude to Mr Peter Mapp of Devizes who has generously given
his time and expertise helping me to present the thesis in the
required format.
I wish to acknowledge the permission of the Controller of
Her Majesty's Stationery Office to quote from publications and
all official records in which the Copyright is vested in the
Crown. I also wish to thank the Librarian of the former TRE
Library at Malvern, now styled the Defence Evaluation Research
Agency, for bringing the history of No 80 (Signals) Wing and Dr
Cockburn's The Radio War to my attention, and also to the
Chief Librarian of the Joint Services Command and Staff
College, Mr Christopher Hobson, for confirming that both
remain unpublished. I am also grateful to the Centre for the
History of Defence Electronics (ChiDE) of Bournemouth
University, which uses the latest information technology to
convey technical and social history in a readily accessible way.
Lastly I should like to thank Air Commodore D.M. Reader, a
former RAF Signals Specialist, for his help and co-operation.
Devizes, Wiltshire July 2002 Peter Lovatt


ii
CONTENTS Page
Submission Details
Acknowledgements i
Contents ii
Maps and Diagrams vii
Glossary viii
VOLUME 1 THE DEFENSIVE PHASE 1
Introduction 2
Chapter 1 Wireless, Signals Intelligence,
Government Code and Cypher School and the Formation of, and Fight for, the Royal Air Force
1. Marconi and the Beginnings of Signals Intelligence
26
2. The Royal Air Force 1919-1933 34
3. Hitler and Enigma 36
4. Radar and the Integrated Air Defence of the UK
40
5. Telecommunications Research Establishment (TRE) and the Start of Radio Countermeasures
48
6. Fighter and Bomber Commands 51
7. Development of Radar in Germany 52
8. Development of Radio in Germany 54
Chapter 2 German Beams and Beacons
1. KGr 100, X-Verfahren and Knickebein 62


iii
CONTENTS Page
Chapter 2 (contd.)
2. Denmark, Norway, the Blitzkrieg and Dunkirk
63
3. Knickebein Revealed 63
4. Luftwaffe M/F Beacons and RAF
Countermeasures 72
5. Formation of No 80 (Signals) Wing 77
6. Target Prediction 78
7. Elektra and Meaconing 84
8. German Avoidance of Meaconing 85
9. Ruffians and Bromides 86
10. Colonel Turner's Department and Starfish
96
Summary 98
Chapter 3 No 80 Wing, RCM Board and TRE
1. No 80 (Signals) Wing, Organisation and Operations
102
2. The Radio Countermeasures Board 124
3. TRE and Radio Countermeasures 126
Summary 128
Chapter 4 New Tactics and Countermeasures
1. German Radar Revealed 132
2. X-Verfahren (Ruffians) and a Change
in Tactics 134
3. HQ No 80 Wing and No 109 Squadron 141
4. Benito Dissected 143


iv
CONTENTS Page
Chapter 4 (Contd.)
5. The Germans Move Eastwards: Operation Barbarossa
146
6. Luftflotte 3 and Expansion of RAF Jamming Capability
147
7. Mediterranean Excursion 149
Summary 151
VOLUME 2 THE OFFENSIVE PHASE 155
Chapter 5 1942 – The Year of the Watershed
1. The Channel Dash 156
2. Freya, Moonshine; Mandrel and Wurzburg
160
3. The Baedeker Raids and Daylight Attacks
166
4. Norwich 8-9 May 1942 167
5. Russian Adventure 174
6. See-Saw, Bernhard and Bernhardine 177
7. TRE at Swanage and Malvern; and the
Sunday Soviets 178
Summary 181
Chapter 6 1943: A Year of Change in Systems and Procedures
1. Knickebein Frequencies and Beam Settings
184
2. A New Use for Knickebein 187
3. The Worrying Increase in Benito 188


v
CONTENTS Page
Chapter 6 (Contd.)
4. Night Attacks, Fighter-Bombers and Cigarette
190
5. A Response to the Fighter-Bomber Threat
191
6. M/F Beacons, Elektra, Sonne and Consol
193
7. The Anti-Jamming Unit 196
Summary 197
Chapter 7 1942 and 1943: The RCM Years
1. Bomber Command's Dilemma 200
2. Kammhuber and German Air Defence 204
3. Airborne RCM – a Start 207
4. Window, First Use and Consequences 214
5. No 101 Squadron 218
6. The Jamming of German Night fighter Communications
219
7. The Rise in German Fighter Strength 223
8. The Hard Road to Berlin 224
9. To Confound and to Destroy 226
10. No 100 Group becomes Operational 229
Summary 232
Chapter 8 1944: Towards D-Day and Beyond
1. Berlin 1944 237
2. Big Week 241


vi
CONTENTS Page
Chapter 8 (Contd.)
3. RCM: Action and Reaction 242
4. No 100 Group: On the Move 247
5. Problems with the Return to Europe 251
6. TRE and Planning for Overlord 253
7. RCM and Overlord 261
8. Air Superiority 270
9. Dispersal: Post-Overlord 271
Summary 272
HQ No 100 Group, Order of Battle, December 1944
275
Chapter 9 Events After D-Day
1. Allied Bomber Operations 276
2. No 80 Wing: Flying Bombs and Rockets 278
3. The Rapidly Changing Strategic Situation
289
4. No 100 Group: RAF and USAAF Operations
291
5. 1945: Operations, Air and Ground 301
Summary 306
HQ Bomber Command Order of Battle,
March 1945 311
Conclusion 313
Bibliography 321


vii
MAPS AND DIAGRAMS Page
1 The Lorenz Beam 56
2 Copy of German Knickebein Document 58
3 Diagram of Benito Beam System 60
4 Hallicrafters S36 67
5 Knickebein Beams Found 21 Jun 40 69
6 Known Knickebein Locations 73
7 Meacons and Enemy Beacons 75
8 GAF Safety Service 87
9 X-Gerät Clock 91
10 Positions of Known Benito Stations 97
10A No 80 Wing's Sites 107
11 Meacon Display Board 109
12 German 53 Cms Radar 135
13 German Long Range Radar 162
14 Mandrel 163
15 Ground Cigar 192
16 TRE RCM Division 257
17 German Radar D-Day 258
18 RCM Plan Overlord 267
19 V1 Campaign against the UK 279
20 V2 Rocket Sites 288
21 Window Areas 297
22 Bomber Command Loss Rate 312


viii
GLOSSARY
A
AAEE Aeroplane and Armament Experimental
Establishment
ABC Airborne Cigar. Countered German VHF
communications on 38-42 Mcs and 30-33 or 48-52 Mcs
ACM Aircraft Transmissions- Meaconing
Abdullah The operation of homing on German Wurzburg
radar stations
ADGB Air Defence of Great Britain, (Fighter
Command)
ADI(Sc) Assistant Director of Intelligence (Science)
AEAF Allied Expeditionary Air Force
AI Air interception by means of radar carried in
fighter aircraft
ALB-15 American British Laboratory, Division 15
(branch of Radiation Research Laboratories working at Malvern)
ASE Admiralty Signals Establishment
Aspirin Purpose built transmitter used as a jammer
again Knickebein navigation and bombing beam
ASV Air to Surface Vessel. Coastal Command search
radar
AVM Air Vice Marshal
Azimuth Vertical arc from zenith to horizon; angular
distance of this from meridian


ix
B
Bagful Automatic search receiver recording RF of
signals and time of interception on tape, with Interchangeable RF heads supplied coverage over 20-2000 Mcs, later 20-6000 Mcs
Barbara and
Barbarossa Development of German Egon control system
Benito German navigation and bombing beam system
in which range is determined by measuring the change of modulation phase of returning signal. Frequencies 42.3-44 Mcs
Benjamin Ground jammer to counter German Y-Gerät
bombing beam
Bernhard German navigation aid using rotating beam,
telemetering is used for communicating to
aircraft
Bernhardine Aircraft equipment associated with Bernhard
Blond Automatic search receiver recording
photographically the pulse shape, pulse length, prf, RF, split speed and time of interception of received signals (Frequency coverage as for Bagful)
Bombe An electro-mechanical device which helped in
the breaking of Enigma messages brought in from the Y-Stations
Bromide Ground jammer to counter German X-Gerät
beam
BSDU Bomber Support Development Unit
Boozer RAF Aircraft receiver giving visual warning
when held in German radar beam
C
Carpet Airborne jammer to counter German Wurzburgs


x
Carpet II Selective noise modulated jammer for 180-450
Mcs and 450-600 Mcs
Carpet III-IV Various types of US barrage jammer
Chain Home CH. Original UK Early Warning radar operating
between 15 and 27 Mcs
Chimney German long range early warning radar
Frequency in the Freya band
CHL Chain Home Low Flying. UK search radar
operating on 200 Mcs
Cigar Airborne selective jammer used against German
night fighter ground control in 38-42 Mcs
Coalscuttle Airborne D/F system for detecting signals on
frequencies above 1000 Mcs
Corona RAF HF ground jammer, used against control
of Luftwaffe night fighters
CRDF Cathode Ray Direction Finder
Crystal
Control
An accurate method of controlling transmitter frequencies by means of crystals
CW Continuous Wave
D
D/F Direction Finding
Dartboard RAF M/F jammer, used against broadcast
instructions to Luftwaffe night fighters
DCAS Deputy Chief of Air Staff
Deviator An emergency jammer deployed employed
against Knickebein, using a 50 watt standard RAF beam approach beacon
Dina(h) US airborne high power jammer
Direction Finding
Method of establishing the bearing of wireless transmitter; two bearings will provide location


xi
Domino Counter to Benito. Signals from aircraft picked
up and re-radiated on ground station frequency
Drumstick RAF jammer used to disrupt Luftwaffe control
channels in the 3-6 Mcs band
Duppel German name for metal foil dropped to confuse
radar. Duppel is a town near the Danish border, where RAF Window was first found
E
Egon German blind bombing system using two Freya
stations
Elektra German navigation system, comprising a fan of
equi-signal beams separated by alternate dots and dashes operating on 481 kcs
ELINT Electronic Intelligence
Erstling German IFF system (FuG 25)
F
Fidget The employment of certain Meacon transmitters
against German beacons broadcasting night fighter commentaries
Fighter Benito Benito German navigation ranging system for
use with Fighter-Bombers
Flensburg German equipment for Homing on to Monica.
Freya German Early Warning ground radar
equipment, originally working on 125 Mcs but later over 75-180 Mcs
Freya Halbe German equipment for Homing on to airborne
Freya jammer
G
GAF German Air Force, the Luftwaffe
GCI Ground Control of Interception (Original RAF
frequency worked on 209 Mcs)


xii
Gee British navigation aid. Aircraft position is
obtained from the intersection of two sets of hyperbolae determined by three ground stations
Gee-H UK blind bombing device. Aircraft equipment
interrogated ground beacons and aircraft position obtained by intersection of two circles (the Gee indicator was used in the aircraft)
Geschwader German Air Force unit, nearest equivalent to an
RAF Group
Gruppe German Air Force unit, nearest equivalent to an RAF Wing. Kampfgruppe 100 was an independent bomber unit and was often referred to as KG 100
GL Gun-laying radar, British Army
Glimmer Code name for seaborne invasion diversion to
Boulogne
Grocer RAF Jamming equipment for Lichtenstein AI
radar
H
H2S Airborne plan position equipment, which
permitted identification of built-up areas and
other landmarks (originally used 10 cms wavelength)
Headache Generic term for measures to jam Knickebein
navigation and bombing beam
Heidelburg German technique for obtaining early warning
using RAF CH transmissions
Heinrich German ground jammer to counter RAF Gee
navigation aid
H/F High Frequency
Himmelbett German system of close-controlled night
fighting
Hoarding German radar equipment for long range early
warning (frequency in the Freya band)
Hohentwiel German ASV working on about 500 Mcs


xiii
I
IFF Identification Friend or Foe
IFRU Intermediate Frequency Rejecter Unit – anti
jamming device
Intruder Fighter interference to enemy aircraft and
airfields, normally at night
J
JG Jagdgeschwader – German Fighter Wing
Jagdschloss German 150 Mcs continuously rotating ground
equipment, with PPI presentation, used for
fighter control
Jostle Airborne frequency modulated jammer for
German R/T
Jostle II Covers 24-54 Mcs
Jostle III Simulated noise jammer using pulse
modulation. Only one model produced
Jostle IV High power frequency modulated jammer,
covering 3-54 Mcs (used for jamming German night fighter R/T control and the V2, when a special variant was used)
K
Kampf
geschwader
KG. German Luftwaffe Bomber Unit equivalent to Royal Air Force Bomber Group
Kampfgruppe KGr. German Luftwaffe Bomber Unit equivalent
to Royal Air Force Wing
Kleine
Heidelberg
Passive German ground system for aircraft detection, using reflected radiation from British
ground radars
Knickebein German navigation and bombing beam. Used
frequencies between 30-33 Mcs


xiv
Korfu German ground radar receiver which provided
bearings to RAF aircraft using H2S
L
Lichtenstein German AI on 90 Mcs, later 36.2-120 Mcs and
490 Mcs
Loran US navigation system similar to Gee, but
operating on 2 Mcs
Lorenz beams Navigational aid employing a split beam to
indicate a given track
M
Magnetron Electron tube for amplifying or generating
microwaves. The Boot and Randall magnetron evolved out of Hertz's original resonant ring,
into a resonant cylinder and thence developed into a six-cavity system
Mandrel Noise modulated Barrage jammer used against
Freyas
Mandrel I Airborne jammer covering 118-148 Mcs, in
bands of 10 Mcs
Mandrel II Airborne jammer covering 60-200 Mcs, in
bands of 25 Mcs
Mandrel III Modified IFF circuit (spot frequency noise
jammer-receiving 15-200 Mcs band)
Mandrel V Improved spot frequency jammer covering 30
600 Mcs
MB Window, designed to cover 70-200 Mcs, Freya
and FuG 220
Mcs Megacycles per second
Meaconing Spoiling German D/F transmissions by picking
up and simultaneously re-radiating the original
signals from a different location
Mimic Operation to upset Luftwaffe radio beacons,
especially when being used to pass information


xv
Mimicry RAF device causing Meacon transmitters to self
oscillate against low-powered Luftwaffe beacons used by aircraft launching flying bombs against the United Kingdom
Monica RAF tail-warning airborne radar equipment
Moonshine Device which enabled one airborne aircraft to
appear as a large formation in an enemy radar
N
Naxos German equipment for homing on to RAF 10
cms equipment fitted to Bomber Command aircraft (FuG 350)
NPL National Physical Laboratory, Teddington
Nuremberg Modification to Wurzburg gun-laying radar to
minimise effects of Window
O
Oboe British blind bombing device using accurate
ground control
Oculist Luftwaffe W/T H/F broadcasts to night fighters
ORS Operational Research Section
Oslo Report One of the most remarkable intelligence reports
of the second world war, sent anonymously to the British Naval Attaché in Oslo in November 1939. It lifted the veil of ignorance which surrounded Germany's most important
scientific and technological advances
Ottakar R/T instructions provided to Luftwaffe night
fighters, initially on 31.2 Mcs
P
PDS TRE Post Design Service


xvi
Perfectos Device enabling British fighters to home on to
emissions of German IFF equipment
Ping Pong A wide band D/F equipment with accuracy of
about a quarter of a degree
Piperack Jamming equipment used against German AI
(Lichtenstein SN2)
PRF Peak Repetitive Frequency
PRO Public Record Office, Kew
PRU Photographic Reconnaissance Unit
R
R/T Radio telephony
Radar Radio Direction and Ranging
RAE Royal Aircraft Establishment, Farnborough
Rayon High-powered RAF transmitter used to
overcome Ottakar
RCM Radio Countermeasures
Rope Non-resonant form of Window, 400 ft rolls of
aluminium foil
RRDE Radio Research and Development.
Establishment at Malvern (formerly ADRDE) Army
RRL Radio Research Laboratories, Harvard, USA,
responsible for research and development on
radio countermeasures
Ruffians British name for X-Verfahren
S
SAT Scientific Adviser on Telecommunications. (Air
Ministry)


xvii
SCR.720 US AI equipment similar to RAF Mk X
Schwan Buoy Luftwaffe navigation beacons provided for
He 111s of 1KG66, employed in air-launching flying bombs over the North Sea
Seetakt German coast watching radar using 370 Mcs
and gun-laying radar
Serrate RAF airborne homing equipment used against
German AI, Lichtenstein and SN-2 radars
SHAEF Supreme Headquarters Allied Expeditionary
Force
Shiver Modified IFF set
SIU Signals Installation Unit closely working with
TRE
SN2 German AI equipment in 90 Mcs band, (later
36.2-120 Mcs)
Sonne German rotating beam navigation system
working on about 30-370 Kcs
Splasher Bomber Command radio beacon
Stopper Patrol Patrol off the entrance to port of Brest, France,
organised by Coastal Command
SWF No 100 Group Special Window Force
T
TAF Tactical Air Force.
Tame Boar Tame Boar GG. Emergency method of
employing Luftwaffe twin-engined fighters in the night defence role
Taxable Code name for invasion diversion to Cap
d'Antifer
Tinsel Airborne selective jammer of German night
fighter control R/T link on 3-6 Mcs


xviii
TRE Telecommunications Research Establishment
Tuba US High-powered ground jammer, used to
counter German Lichtenstein radar
V
V1 German flying bomb
V2 German long range rocket
VHF Very High Frequency, in the RAF 30-300 Mcs
W
Wassermann German early warning radar
WIDU Wireless Intelligence and Development Unit
Wild Boar Wild Boar. Emergency method of employing
Luftwaffe day fighters in the night defence role
Window British name for metal foil dropped to confuse
German radar organisation
Windjammer RAF name for Bernhard and Bernhardine
W/T Wireless Telegraphy
Wurzburg German ground radar equipment on about 53
Mcs, used to direct AA guns, searchlights and nightfighters


xix
X
X-Gerät Airborne apparatus associated with
X-Verfahren
Y
Yagi Type of aerial display developed by Dr. Yagi of
Japan, exemplified by TV aerials utilised for the reception of UHF transmissions
Y-Control German method of controlling nightfighters
using modified Y-Gerät equipment
Y-Gerät German beam used for navigation and blind
bombing


1
VOLUME ONE OF TWO
THE DEFENSIVE PHASE


2
INTRODUCTION.
When Britain declared war on Germany in 1939, the United
Kingdom little realised how much the Luftwaffe had come to
depend on Medium Frequency radio beacons for navigation
purposes, although it was aware of their existence and of their
routine employment by Lufthansa, the national state airline, for
such use in peacetime. What was not known, however, was the
development of the three radio navigation and bombing beams,
in the use of which German aircrews had already received, or
were about to receive, appropriate training. No other air force in
the world possessed such beams and thus, when the United
Kingdom began to be attacked in earnest in 1940 by the
Luftwaffe making use of these devices, it caused some
consternation in London. The Royal Air Force reacted to the
situation by seeking out methods with which to counteract
them, firstly by masking the beacons with equipment already
developed by the General Post Office, and then by attempting to
jam the beam signals. Without suitable equipment to hand,
however, makeshift measures had to be adopted against the
latter, until purpose-built transmitters became available at a
later date, from the Telecommunications Centre. During 1940
until early in 1942, the Royal Air Force fought a defensive radio
countermeasure war against Germany. This period, the
defensive phase of the early years of the war, is the focus of the
first part of this thesis.
So important had the Benito countermeasures become by
1941 that the RAF considered it necessary to issue Secret


3
Benito Operations Reports from 8 March 1941 to 17 April 1941.
These may be found in the Public Record Office at Kew, under
the reference Air 40 Piece 2242 and provided much of the
evidence on which this account is based.
From 1942 onwards, after the Channel Dash, when the
German Battle Cruisers Scharnhorst and Gneisenau and Cruiser
Prinz Eugen, successfully passed through the English Channel
on their way to Germany, the situation changed. For the first
time in the war, the Germans had jammed British radar and
thus there were no longer the inhibitions and restraints which
had formerly held back the Royal Air Force from such actions in
the past. Until that point the British had been extremely
sensitive over the Chain Home radar and thus restrained from
interfering with German radar in any way. Moreover, Bomber
Command was beginning to become a stronger and more
effective force in the same year, 1942, which the United States
Army Air Forces started to arrive in Europe, although some time
was to elapse before the latter would be able to attack Germany
effectively. But as bomber operations conducted by the Royal
Air Force started to increase in size and tempo, losses began to
mount due to effective German defences, which increasingly
involved the use of radar, and radar controlled searchlights and
guns and radar equipped night fighters. Consequently, in order
to try to reduce the numbers of casualties, Bomber Command
sought to employ the first of what was to be a range of airborne
countermeasures. Ground measures had already been utilised
for this purpose but invariably these were limited by range.
Thus, the next step was to provide airborne equipment for the


4
task. Unfortunately, some of the items were bulky and heavy
and thus a weight penalty was involved; more protection – less
range or bomb load. Eventually a compromise was reached,
whereby some countermeasure protection was carried by a
majority of aircraft, with the heavier equipment being allocated
to special support aircraft dedicated to the provision of radio
countermeasures. The period 1942-1945 thus marks the second
stage in the evolution of the radio war, or defensive-offensive
phase, in which ground and airborne equipment contributed to
the radio war, and is the subject of Volume Two of this thesis.
1. Aims of the Thesis
From intercepted Enigma messages, and the interrogation
of captured Luftwaffe aircrew, together with the aid of German
maps and documents, the Royal Air Force confirmed that in
1940 the German Luftwaffe were using wireless beacons and
beams for navigation and bombing purposes. The first aim of
this thesis is thus to explicate the search for, and the finding of,
these particular beacons and beams by the RAF. Once these
beacons and beams were found and identified, the Air Ministry
decided to take action in order to render them useless for the
purpose intended. To be successful, however, such measures
had to be controlled and applied in a logical manner. In order to
be able to achieve this a new formation was created, No 80
(Signals) Wing. The second aim of the thesis is thus to examine
the reasons why this Wing was formed, to investigate its
organisation and operations; and to confirm how it was
controlled.


5
In 1939 the Royal Air Force possessed little in the way of
radio jamming equipment; if countermeasures were to be
applied against the German devices in 1940, the Royal Air Force
would have to improvise. Later on, dedicated jammers would be
designed and made available. The third aim of the thesis is thus
to trace the early and subsequent ground-based measures
taken to nullify the German beacons and beams; and to
determine just how successful No 80 Wing was during the
defensive phase in the radio war.
Inevitably, the effects of ground-based jamming equipment
were limited by range. In order to overcome this disadvantage
thought was given to RAF aircraft carrying their own airborne
jammers. At first Bomber Command was loath to adopt such
measures, as indeed it had been, earlier, with radio navigation
and target-finding equipment, for fear of disclosing the aircraft's
position. It will be shown that rising losses, however, forced the
acceptance of defensive radio equipment. Moreover, in 1942, the
Germans jammed British radar to expedite the passage of their
capital ships through the English Channel. This action enabled
the RAF to adopt a more offensive stance in the radio war and to
jam German radar. In order to control the defensive and
offensive aspects of the radio war, the RAF decided late in 1943
to establish a new formation, No 100 Group, which would be
responsible for all such measures, including the activities of
No 80 Wing. The fourth aim of this thesis is to discover how and
why this Group was formed, to investigate its organisation and
to appraise the success and failure of its operations.


6
The Telecommunications Establishment (TRE) evolved out
of previous Air Ministry Research Stations, associated with the
development and provision of the radar chain, which provided
warning of hostile aircraft approaching the United Kingdom; the
Chain Home and Chain Home Low. TRE came to be responsible
for designing much of the jamming equipment required by the
RAF, and for producing many of the prototype transmitters. TRE
also submitted a number of authoritative papers on future radio
countermeasure policy to the RCM Board in London. The fifth
aim of this thesis is to examine the contribution made by this
research establishment to the radio war, and especially the
assistance provided to the Bomber Offensive and the radio
countermeasure plan implemented by the allies on D-Day,
6 June 1944.
2. Literature Consulted
A large number of unpublished primary sources were
consulted in the writing of this thesis. Of particular interest in
the Public Record Office was the lengthy, unpublished No 80
Wing Historical Report written by the staff officers concerned
with No 80 Wing's activities in January 1946, with a Foreword
by the then Officer Commanding No 80 Wing, Group Captain
E.B. Addison.1 In addition the unpublished monograph, The
Radio War, written by Dr Robert Cockburn on the subject as
seen from the Telecommunications Research Establishment's
1 No 80 Wing, Royal Air Force Historical Report 1940-1945, PRO Air 41/46.


7
point of view proved invaluable.2 Both sources have been
consulted and quoted at length. No official history of No 100
Group has been published and no draft of one could be found in
the PRO, and this thesis therefore fills an important gap. But an
operational history has been written and published by Martin
Bowman and Tom Cushing, which provides useful detail about
the activities of the Group’s Mosquito force.3 A history of TRE
has been written, but not published and a draft copy reposes in
the former TRE Library at Malvern, now the Defence Evaluation
Research Agency.
I found the registered papers belonging to the Department
of Chief of the Air Staff under Class Air 8 helpful. Both Bomber
Command's papers under Class Air 14 and Fighter Command's
papers under Air Class 16 I found invaluable in understanding
the radio war. The unregistered papers belonging to Class Air 20
was also essential reading. Classes Air 24, 25, 26, and 27
provided basic information about operations undertaken by the
RAF Commands, Groups, Wings and Squadrons. Class Air 40
contained intelligence information concerning secret Benito
activity and Class Air 41 contained Monographs and Narratives
written by the Air Historical Branch, which are also essential
reading if the radio war is to be understood. All of these may be
2 The Radio War, PRO Air 29/8953.
3 Martin W. Bowman and Tom Cushing, Confounding The Reich The Operational History of 100 Group (Bomber Support) RAF (Patrick Stephens Limited, Yeovil, Somerset, 1996).


8
found in the Public Record Office at Kew, under the references
furnished, and provide much of the evidence on which this
account is based. Vital information about the Government Code
and Communications Centre was obtained by reading Class HW
43, the Birch Histories. Classes Avia 7 and 26 provided much
detail about the work of TRE. Appendix "E", the RCM section of
the Harris War Despatch (PRO Air 20/1962) was especially
informative about the development of Radio Countermeasures
in Bomber Command.4 F.H. Hinsley's, British Intelligence in the
Second World War, 4 vols. was particularly revealing, Volume 1
providing much information about the Oslo Report, the GAF
raid on Coventry and the breaking of the Enigma Code.5
From secondary sources the Most Secret War by Dr R.V.
Jones is essential reading to an understanding of the whole
campaign, as is Instruments of Darkness by Alfred Price.6 RAF
Bomber operations are comprehensively covered in Martin
Middlebrook and Chris Everitt's excellent The Bomber Command
War Diaries and Martin Streetly's Confound and Destroy
provides much technical detail about No 100 Group, including
4 PRO Air 20/1962, Despatch on War Operations 23 February 1942 – 8 May 1945 by Air Chief Marshal Sir Arthur T. Harris, G.C.B., O.B.E., A.F.C. Air Officer Commanding-in
Chief, Bomber Command. But see also Despatch on War Operations 23 February 1942 to 8 May 145, by Sir Arthur T. Harris (Frank Cass, 1995)
5 F.H. Hinsley, British Intelligence in the Second World War, 4 vols (HMSO, 1979) 1.
6 R.V.Jones, Most Secret War (Hamish Hamilton, 1978); Alfred Price, Instruments of Darkness (Macdonald and Jane's 1977).


9
the American dimension and the bomber support campaign.7
Air Vice Marshal Tony Mason in his Air Power: A Centennial
Appraisal, provided useful information about the infant Royal
Air Force and Luftwaffe.8 The same author, Tim Mason, in his
British Flight Testing, confirmed that aircraft from the Aeroplane
and Armament Experimental Establishment were placed at the
disposal of Orford and Bawdsey research stations from 1936, for
the purposes of developing airborne radar.9 Air Vice Marshal
R.A. Mason in his Air Power: An Overview of Roles, endorses the
importance of Early Warning.10 As Tim Mason, in The Secret
Years, he brings out the secretive nature of the work of the
Wireless Investigation and Development Unit (later No 109
Squadron) whilst at Boscombe Down.11
The most comprehensive discussion of Hitler’s strategic
thinking is to be found amongst Germany and the Second World
War edited by the Research Institute for Military History,
Potsdam, Germany; volumes IV, The Attack on the Soviet Union
7 Martin Middlebrook and Chris Everitt, The Bomber Command War Diaries (Viking Books Ltd, 1985); Martin Streetly, Confound and Destroy (Jane's, 1985).
8 Air Vice Marshal Tony Mason, Air Power: A Centennial Appraisal (Brassey’s 1994).
9 Tim Mason, British Flight Testing (Putnam, 1993).
10 Air Vice Marshal R.A. Mason, Air Power: An Overview of Roles (Brassey’s Defence Publishers, 1987).
11 Tim Mason, The Secret Years (Hikoki Publications, Aldershot, 1998).


10
and VI, The Global War being especially useful.12 The Rise and
Fall of the Luftwaffe, by David Irving, provides a good account of
the fortunes of the German Air Force; while Gebhard Aders in
his History of the German Night fighter Force, drawing on such
archival sources as the Bundesarchiv/Militärarchiv, Freiburg,
describes in detail some of the varying successes and failures of
Bomber Command's attacks on German targets.13 The Luftwaffe
War Diaries by Cajus Bekker, translated and edited by Frank
Ziegler, is based on interrogations of numerous wartime
Luftwaffe leaders, and is useful in that it gives an overall view of
the activities of the German Air Force in the west, including the
period covering the Battle of Britain, the Night Defence of the
Reich and the Battle of Germany.14 Most helpful with details of
the Luftwaffe Pathfinder beam operations over the United
Kingdom was Ken Wakefield's Pfadfinder and E.R. Hooton in his
Eagle in Flames which furnished information about German
casualties and losses.15 Donald L. Caldwell's JG 26, based on
12 Rolf-Dieter Müller, ‘From Economic Alliance to a War of Colonial Exploitation’ in Research Institute for Military History, Potsdam, Germany (eds.) Germany and the Second World War, Vol. IV, The Attack on the Soviet Union, and Werner Rahn, ‘The War at Sea in the Atlantic and in the Arctic Ocean’ in Research Institute for Military History, Potsdam,
Germany (eds.) Germany and the Second World War: Vol. VI, The Global War (Clarendon Press, Oxford, 2001).
13 David Irving, The Rise and Fall of the Luftwaffe (Little, Brown and Company, BostonToronto, 1973); Gebbard Aders, History of the German Night fighter Force 1917-1945 (Crecy Books, Somerset, 1992).
14 Cajus Bekker, The Luftwaffe War Diaries (Macdonald, 1966).
15 Ken Wakefield, Pfadfinder (Crecy Books, Norwich, 1992); E.R. Hooton, Eagle in Flames (Brockhampton Press, 1999).


11
the recollections of fifty German veterans, provided an insight
into the operations of the leading Luftwaffe fighter wing when it
was based in France. His descriptions of the Channel Dash and
the GAF response to the allied landings on D-Day were
especially illuminating.16
Michael Howard's British Intelligence in the Second World
War: Finest Hour, was useful in that Chapter 6 provided details
about Operation Fortitude and discussed the lengths to which
the British were prepared to go to mislead Hitler about the
landing beaches on the Continent.17 Inside the Third Reich by
Albert Speer provided an insight into the way that Germany was
governed and how he, Speer, dealt with shortages of
armaments, aircraft and fuel, often at a critical time.18 Stephen
E. Ambrose's, The Wild Blue, provided an indication of the
damage done to the German aircraft factories during Operation
Big Week, as well as the grievous losses inflicted on the United
States Army Air Force by the German fighters.19 Reg Batt, in his
Radar Army, provided the information that Metropolitan Vickers
produced the Chain Home radar transmitters working on 6-15
metres and that A.C. Cossor of London produced the Chain
16 Donald Caldwell, JG 26 (Orion Books, New York, 1991).
17 Michael Howard, British Intelligence in the Second World War: Finest Hour, vol.5, (HMSO, 1990) 5.
18 Albert Speer, Inside the Third Reich (Weidenfeld & Nicolson, 1970).
19 Stephen, E. Ambrose, The Wild Blue (Simon and Schuster, New York, 2001).


12
Home Receivers.20 E.G. Bowen's, Radar days provided a useful
insight into the early days of Air Interception, together with a
fascinating over-view of the Tizard Mission to the USA and
Canada, with its gift of the Magnetron and jet engine.21 The
beginning of No 80 (Signals) Wing, and the early radio
countermeasures, are well described in Laurie Brettingham's
Royal Air Force Beam Benders, 80 (Signals) Wing, 1940-1945
using Air 26/280, 26/580, 27/853 and 41/46 as sources; and
John R. Bushby's Air Defence of Great Britain, details some of
the problems experienced in the United Kingdom when the
Authorities tried to arrive at a fully integrated system of air
defence.22 The importance of the convoys to Russia and how
crucial it was to keep Stalin in the war against Hitler is well
brought out in Martin Gilbert's Finest Hour.23 In Barbarossa,
Alan Clark relates how perilously close the German army came
to capturing Leningrad and possibly forcing Stalin to sue for
peace.24 The bombing of London, especially on the night 29
December 1940, is well documented in Basil Collier's The
Defence of the United Kingdom, the main Ruffian beams used on
20 Reg Batt, The Radar Army (Robert Hale, 1991).
21 E.G. Bowen, Radar Days (Adam Hilger, Bristol, 1987).
22 Laurie Brettingham, Beam Benders, Royal Air Force 80 (Signals) Wing 1940-1945
(Midland Publishing Limited, Leicester, 1997); John R. Bushby, Air Defence of Great Britain (Ian Allan, 1973).
23 Martin Gilbert, Winston S. Churchill Finest Hour 1939-1941, 6 vols. (Houghton Miflin Company, Boston, 1983),6.
24 Alan Clark, Barbarossa: The Russian-German Conflict 1941-1945 (Orion Books, 1966).


13
that occasion being of special interest.25 Aileen Clayton provides
an early and fascinating account of the RAF Y-Service, and also
describes the inter-change of information between Cheadle and
Kingsdown in her The Enemy is Listening.26 Alan W. Cooper well
describes the use Corona and Airborne Cigar are put to, in his
Bombers over Berlin.27 The history of No 109 Squadron is
portrayed in Michael Cumming's Beam Bombers, starting with
WIDU, progressing through 109 Squadron and ending with
Oboe operations in No 8 (PFF) Group.28 Len Deighton in his
Blitzkrieg discloses that the Scharnhorst and Gneisenau were
fitted quite early with the latest German radar (Seetakt) and
that in November 1939 this enabled them to steam through
Royal Naval patrol lines in daylight.29 Jeffrey Ethell and Alfred
Price in their Target Berlin confirm that the B-17 and B-24
pathfinders of 482nd Bomb Group were fitted with the British
H2S or its American derivative H2X, radar, enabling them to
bomb through cloud.30 Adolf Galland in his The First and Last
provides a first hand account of the Channel Dash, thus giving
an indication of the thoroughness of the German preparations
25 Basil Collier, The Defence of the United Kingdom (HMSO, 1957).
26 Aileen Clayton, The Enemy is Listening (Crecy Books Limited, 1993).
27 Alan W. Cooper, Bombers Over Berlin (Patrick Stephens, 1989).
28 Michael Cumming, Beam Bombers (Sutton Publishing, Stroud , 1998).
29 Len Deighton, Blitzkrieg (Grafton Books, 1990).
30 Jeffrey Ethel and Alfred Price, Target Berlin (Book Club Associates, 1981).


14
for the transit.31 Derek Howse in his Radar at Sea mentions the
remarkable fact that a large convoy of merchant ships sailed
through the Dover Straits at 5pm on D-Day in broad daylight,
the first convoy to do so for four years.32 David Irving provided
much useful material about the German V1 and V2 in his The
Mare's Nest.33 Derek E. Johnson in his East Anglia at War
1939-1945 gave helpful background information on the German
raid on Norwich, when No 80 Wing engaged the attacking
aircraft with radio countermeasures.34 Life and work at RAF
Defford, the airfield allocated to TRE, was well described by
Albert Shorrock in Pioneers of Radar by Colin Latham and Anne
Stobbs.35 The same authors in Radar: A War Time Miracle,
provided an explanation as to how Gee worked and gave an
example of how Gee-H was used on D-Day by No 218 Squadron
when Window was required to simulate an invasion fleet.36 The
secrets of the Bruneval Raid were disclosed in George Millar's
account of the British raid on a German radar station; parts of
the German radar were subsequently brought back to England
for investigation by RAE at Farnborough.37 In his Why The Allies
31 Adolf Galland, The First and Last (Methuen and Company, 1970).
32 Derk Howse, Radar at Sea (Macmillan, 1993).
33 David Irving, The Mare's Nest (William Kimber and Company Limited, 1964).
34 Derek E. Johnson, East Anglia at War (Jarrold, Norwich, 1994).
35 Colin Latham and Anne Stobbs, Pioneers of Radar (Sutton Publishing, Stroud, 1999).
36 Colin Latham and Anne Stobbs, Radar (Alan Sutton, Stroud, 1996).
37 George Millar, The Bruneval Raid (The Bodley Head, 1974).


15
Won Richard Overy pays tribute to Joseph Kammhuber's
organisation of German air defence, mentions the devastating
effect of Window and other countermeasure devices and also
describes the advent of the new long-range allied fighter, the
North American Mustang fitted with a Rolls-Royce engine.38
Simon W. Parry presents an interesting picture of Operation
Gisela and of German aircraft appearing over the United
Kingdom on the night 3-4 March 1945.39 Murray Peden, a
Canadian, provides a fascinating account of life as a pilot on No
214 Squadron, engaged on countermeasure duties.40 In the
Design and Development of Weapons, M.M. Postan, D. Hay and
J.D. Scott, explain the Doctrine of Quality and how it had to be
dispensed with during the period of expansion and rearmament
in 1934 and 1935; they then go on to explain the development
of radar in the United Kingdom.41 Germany's pioneering
achievements, 1904-1945, are set out in The Radar War, by
David Pritchard; the high technical standard of the equipment
and the low standard of German radar operators is neatly
brought out.42 Henry Probert in his Bomber Harris His Life and
Times, mentions the valid point, made by Albert Speer, that the
38 Richard Overy, Why the Allies Won (W.W. Norton and Company, New York, 1997).
39 Simon W. Parry, Intruders Over Britain (Air Research Publications, Surbiton, 1987).
40 Murray Peden, A Thousand Shall Fall (Imperial War Museum, 1981).
41 M.M. Postan, D. Hay, .D. Scott, Design and Development of Weapons (HMSO, 1964).
42 David Pritchard, The Radar War: Germany's Pioneering Achievements 1904-1945 (Patrick Stephens Ltd, Wellingborough, 1989).


16
real importance of the air war consisted in the fact that it
opened a second front long before the actual invasion of Europe
occurred in June 1944.43 The Night Blitz 1940-1941, by John
Ray, interestingly goes over the reasons why the Luftwaffe was
forced to turn to night bombing towards the end of 1940, at the
end of the Battle of Britain.44 Michael Renaut's Terror by Night
is written by a former 100 Group Squadron Commander and
provides much information about raising a radio
countermeasure unit; he also disclosed that he owed his life to
taking a scratch crew on operations, instead of his regular and
more experienced one.45 Frank Rowlinson explains in his
Contributions to Victory how Metropolitan Vickers Electrical
Company was able to introduce new design shops and thus help
to design and make radio countermeasure equipment for the
first time.46 Bob Ruegg and Arnold Hague in Convoys to Russia
1941-1945, were able to assess the strength and pinpoint the
location of the German Air Force units based in North Norway,
quite accurately, and estimate the dangers to Allied convoys
from such a force.47 Station X by Michael Smith tells the story of
the Codebreakers of Bletchley Park; it draws attention to the
43 Henry Probart, Bomber Harris: His Life and Times (Greenhill Books, 2001).
44 John Ray, The Night Blitz 1940-1941 (Arms and Armour Press, 1996).
45 Michael Renaut, Terror by Night (William Kimber and Company Limited, 1982).
46 Frank Rowlinson, Contributions to Victory (Metropolitan Vickers Electrical Company Limited, Manchester, 1947).
47 Bob Ruegg and Arnold Hague, Convoys to Russia 1941-1945 (World Ship Society, Kendal, 1992).


17
important connection between Station X and the RAF Y-Service
units, Kingsdown and Cheadle.48 In Enemy below!, Ted Sweet
gives an excellent account of the Meaconing activities at
Mundesley, in Norfolk, which was also the location of a Bomber
Command and US Army Air Force Splasher Station.49 B.L. Villa
in Unauthorised Action describes the poor planning of the
Dieppe raid, when the RAF lost 106 aircraft and mentions the
fact that Mountbatten borrowed a number of Gee navigation
devices from Sir Arthur Harris at Bomber Command for use by
the ships taking part in the raid.50 In GCHQ, The Secret Wireless
War 1900-86, Nigel West explores the world of the RAF SIGINT
Organisation, No 80 (Signals) Wing, RAF Countermeasure
transmitters and the Enigma Intercept Stations.51 In Attack
Warning Red Derek Wood provides a history of air defence of the
British Isles, bringing in the Observer Corps and the 1939 Air
exercise, when radar tracks were married with visual sightings
from the ground for the first time; he goes on to emphasise the
importance of an integrated air defence system.52 He also, in his
The Narrow Margin, provides a clear account of the Battle of
48 Michael Smith, Station X (MacMillan Publishers Ltd, 1998).
49 Ted Sweet, Enemy below! (Square One Publications, Worcester, 1991).
50 B.L. Villa, Unauthorised Action: Mountbatten and the Dieppe Raid (OUP, Ontario, 1989); Werner Rahn, ‘The War at Sea in the Atlantic and in the Arctic Ocean’ in Research Institute for Military History, Potsdam, Germany (eds.) Germany and the Second World War: Vol. VI, The Global War, p. 441
51 Nigel West, GCHQ: The Secret Wireless War (Weidenfeld and Nicolson, 1984).
52 Derek Wood, Attack Warning Red (Macdonald and Jane's, 1976).


18
Britain and includes the latest and most authoritative list of
Luftwaffe losses published so far. He goes on to relate the
development of radar for the German Navy 1934-35 and for the
other German services shortly thereafter. He goes on to mention
the German beams and the formation of No 80 (Signals) Wing.53
The BBC Video, The Secret War, discusses the battle of the
beams and introduces such personalities as Dr R.V. Jones, T.L.
Eckersley of the Marconi Company, who was the country's
leading expert in radio propagation, and E.A.B. Addison. In the
video R.V. Jones makes the point that twenty-one factories were
destroyed at Coventry and if the Luftwaffe bombing beams had
not been overcome, the Rolls-Royce aerofactory at Derby and
others were likely to have gone the same way with consequent
disastrous results for Britain.54
Much has been written and published about radio
countermeasures, but in order to understand the radio war
fully, it is necessary to be aware of the contribution made by
each of the key components. Thus it is essential to learn of
No 80 (Signals) Wing and how and why it was created; how the
Y-Service was able to provide this formation with the necessary
intelligence, essential to its operations. How the success of
No 80 Wing’s operations led to the formation of No 100 Group,
in order to control all radio countermeasures, ground as well as
53 Derek Wood, The Narrow Margin (Tri-Service Press Limited, 1990).
54 BBC Video, The Secret War (BBC Enterprises Limited, 1994), 2 vols., 1 BBC V5339.


19
air, and above all, how the Telecommunications Research
Establishment came to provide the new and original hardware
with which to fight the campaign, together with the necessary
policies on how best to use it. This thesis therefore goes beyond
what is already known.
3. Thesis Lay-out
In order to set the scene for the thesis, the first chapter
recalls how practical wireless first came to Britain in 1896, in
the hands of Marconi, and how his apparatus came to be
accepted by the Royal Navy. It is also important to stress that
wireless was an open method of communicating and hence it
was considered necessary to use codes and cyphers: moreover,
wireless was also subject to intentional interference or jamming,
it was noted as early as 1914.55 The chapter goes on to relate
how great advances were made during World War One in the
techniques of decryption and especially Direction Finding and,
how at the end of hostilities, the Government Code and Cypher
School was created. A brief description then follows of the
struggle to maintain the Royal Air Force as a separate service
between the years 1919-1933; as it ended, Hitler arrived on the
scene in Germany: shortly the early models of Enigma, the
commercial models of which were already in use, began to be
issued to the German armed forces. The beginnings of radar in
the United Kingdom are then explored and the importance of an
55 Nigel West, GCHQ, p.18.


20
integrated air defence system emphasised. The chapter goes on
to stress how much the Royal Air Force came to rely on the
Telecommunications Research Establishment.
Chapter Two opens by describing the training of Luftwaffe
aircrews in the use of X-Gerät, before the commencement of
hostilities in 1939 and of Knickebein and X-Gerät after that
date. Enigma disclosed the existence of Knickebein to the
British in May and June 1940 and how later in June the beams
were found laid over the United Kingdom. In July it was
confirmed that the Germans were using Medium Frequency
radio beacons for navigation purposes while over the United
Kingdom. RAF Meacons, transmitters designed to re-radiate the
enemy beacon signals, were then introduced to combat the
German beacons with great success. No 80 (Signals) Wing was
formed to control all the measures being taken against the
beams and beacons. It then became apparent that British
countermeasures would have to be monitored for their
effectiveness. This task was largely given to the aircraft of the
Wireless Investigation and Development Unit. Further Luftwaffe
navigation aids were uncovered such as Elektra. The Germans
then took steps to avoid RAF Meaconing; and the Chapter ends
with the uncovering of the third Luftwaffe beam, Benito,
together with an account of the activities of Colonel Turner's
Starfish department of the Air Ministry.
Chapter Three is concerned with the organisation and
operations of No 80 (Signals) Wing in detail. It points out the


21
advantages of establishing a good liaison with Fighter
Command; and introduces the work of the Radio
Countermeasures Board, which approved national policy and
was the final arbiter whenever disputes arose between users of
countermeasures. The Chapter ends by investigating some of
the early measures taken by No 80 Wing.
Chapter Four discloses how Seetakt, the German coastal
radar, came to be identified and how this event led to the
uncovering of the early warning radar Freya. Further
information about Wurzburg, the accurate height-finding radar,
was then obtained by radio investigative flights that took place
over France. More and more, the Germans were now seeking to
avoid British countermeasures and their tactics are explained,
along with the RAF attempts to bomb the German transmitters
sited on the Cherbourg peninsula. The third German beam,
Y-Verfahren, meanwhile remained under investigation by the
Research Establishments, and it was during February 1941,
that the first RAF countermeasure, Domino, was produced for
Y-Verfahren. The X-Verfahren or Ruffians were used less in
June 1941, although the system continued to be employed until
withdrawn in the following July. Further information about the
work undertaken by No 109 Squadron (formerly WIDU) is then
provided. The detailed working of Benito now became available,
resulting in the evolution of the second Benito jammer,
Benjamin. The remainder of the Chapter provides an account of
the rundown of the Luftwaffe in the west; the expansion of RAF


22
jamming capability; and a late flurry of beacon and Meacon
activity.
Chapter Five deals with the escape of the German Battle
Cruisers Scharnhorst and Gneisenau through the English
Channel, when British radar was jammed for the first time. It
goes on to list the first RAF airborne devices, Moonshine and
Mandrel, and how they were employed. The Chapter continues
with the German Baedeker Raids on the United Kingdom and
the raid on Norwich together with No 80 Wing's reactions. No 80
Wing's short excursion to northern Russia is then revealed; and
the Chapter ends with reference to the newly introduced
controls for German night fighters and the work being
undertaken by TRE at Swanage and Malvern.
Chapter Six covers the low level of Luftwaffe activity over
the United Kingdom during the latter half of 1942; this became
more active in 1943, when German fight-bomber attacks
started. The Germans then found a new use for Knickebein, and
this was accompanied by a worrying increase in the number of
Benito stations, which forced No 80 Wing to redistribute its
transmitters. Night attacks then resumed against the United
Kingdom; No 80 Wing responded successfully by using the
jammer, Cigarette.
Bomber Command's failure to find its targets and bomb
them accurately is brought out in Chapter Seven; it goes on to
show how these shortcomings were overcome. A new
commander was able to introduce techniques with the radio


23
aids developed by TRE and so help to secure the future of the
Command. Germany's improved air defences under the
guidance of General Kammhuber then come under scrutiny;
these improvements led to rising losses, forcing Bomber
Command to adopt radio countermeasures for protection
purposes. One of the measures used was Window; it was so
successful that it caused a revision to the whole German night
fighter system. It was important for Bomber Command to
possess up-to-date and detailed knowledge of the latest German
defences and here No 101 Squadron, with an electronic
monitoring role, was of assistance. No 80 Wing, too, continued
to play a part in the struggle. A series of British attacks against
Berlin started in November 1943 and, as the loss-rate continued
to rise, it was decided to form a new formation to bring together
the application of manifold countermeasures under one
authority. This was No 100 (Bomber Support) Group.
Chapter Eight continues with RAF attacks on Berlin and
goes on to explain how, prior to the invasion of France, it was
necessary for Bomber Command to attempt to hit small targets
accurately by night. This it did successfully, somewhat to its
surprise. As the RAF Berlin campaign drew to a close, the
USAAF started to assault the German aircraft industry. The
somewhat laborious task of creating an entirely new Group, in
the middle of a war, is then covered together with the work of a
small but significant unit of the USAAF. The Chapter ends with
an investigation into TRE's contribution to the RCM Plan for
Operation Overlord, the Plan being made by possible by the


24
massive air superiority now available to the RAF and United
States Army Air Forces.
After the successful landings in France, in June 1944, the
strategic air force concentrated on supporting the allied land
force, but with capacity to spare the German oil industry was
also attacked. The German flying bomb and rocket attacks then
started, when No 100 Group's ground and air jammers were
able to make a contribution. The remainder of the Chapter is
taken up with a description of the continuing Bomber
Command attacks on German targets and the level of
sophistication of the feints, ruses and diversions necessary in
order to keep main force aircraft losses to a minimal level.
The Royal Air Force countermeasure organisation was
formed at a perilous time for the United Kingdom in 1940. It
was facing invasion daily with an army at home that had
recently been ejected from the Continent, and largely bereft of
its heavy weapons and equipment. Only the RAF was available
to stand up to the Luftwaffe and so guarantee the safety of the
British way of life. It was at this juncture that the Luftwaffe
beacons and beams were found, dealt with and eventually
mastered. This was not an easy undertaking. Firstly an
organisation had to be improvised, equipment found and
communications established, tasks not easy in the middle of a
war, and which were to take time. The Research Establishments
had to be approached and inducted into the requirements of No
80 Wing. Fortunately TRE was available, willing to assist and


25
well-versed in RAF ways and procedures. However, all of this
would not have been enough without intelligence, some of it
high level, only obtainable from Ultra; the remainder fortunately
could be acquired from RAF and national sources. By February
1942, as the defensive phase gave way to a more offensive spirit,
German radar was jammed. And so began a period when first
one side, then the other gained ascendancy in the radio war. It
soon became obvious that as Bomber Command started to
employ more and more electronic aids and countermeasures,
another RAF controlling formation would be required. Hence
towards the end of 1943, No 100 (Bomber Support) Group was
formed and charged with the responsibility of providing all radio
countermeasures to the RAF. Fortunately, when it was time to
return to Europe in June 1944, the allies had established air
superiority, and although radio countermeasures on the day
were used to blind some German radars, they were largely
employed on protecting allied aircraft and implementing
successfully a number of deception plans. From this time
onwards to the end of the war, countermeasures were employed
almost exclusively on the protection of RAF and United States
Army Air Force bomber aircraft, and notably in covering the
D-Day landings.


26
CHAPTER ONE: WIRELESS, SIGNALS INTELLIGENCE, GOVERNMENT CODE AND CYPHER SCHOOL AND THE FORMATION OF, AND FIGHT FOR, THE ROYAL AIR FORCE
1. Marconi and the Beginnings of Signals Intelligence
During the Nineteenth Century, the Admiralty had long wished
to be able to communicate with HM ships at sea quickly and
accurately, especially with those out of sight of land. Great interest
was thus taken in Marconi and his new development, wireless,
when he arrived in Britain in 1896.1 During the next few years he
attempted to improve the performance of his equipment, while
conducting a series of major demonstrations in order to convince
the interested and indifferent alike of the advantages of using
wireless as a means of conveying and receiving information.
Representatives of the Admiralty were present at a trial held in
1899 when for the first time signals in morse code were passed by
wireless from England to France over a distance of 32 miles. The
Royal Navy was impressed, as were members of the public. The
military authorities however, remained lukewarm, much preferring
to continue to use telephone lines and telegraph. Shortly,
transmitters and receivers were installed in two of HM ships, which
were able to communicate successfully with one another while at
sea and some 85 miles apart. A year later, and after a further
increase in range, the Admiralty placed a contract with Marconi for
exclusive rights to his equipment.2 Notwithstanding the legal
niceties of this arrangement, the Army then proceeded to construct
1 Frances Donaldson, The Marconi Scandal (Rupert Hart-Davis, 1962) p.11; Nigel West, GCHQ: The Secret Wireless War, pp.6-7.
2 Nigel West, GCHQ: The Secret Wireless War, pp.10-12.


27
its own Marconi field wireless station. The subsequent trial,
however, held in South Africa during the Boer War, was
unsuccessful and the equipment was handed over to the Royal
Navy, who gratefully and promptly made full use of it. In due
course, and to facilitate communication with the fleet, the
Admiralty placed an order with the Marconi Company for a number
of shore stations to be erected in England and Ireland and, at the
same time, it decided to equip some twenty-six warships with
wireless apparatus. While work proceeded with these contracts,
wireless signals were sent across the Atlantic from the Marconi
transmitter situated at Poldhu, in Cornwall and successfully
received in Newfoundland. Once the fleet was fitted with wireless
the Admiralty would be able to keep in touch with its ships at sea
for the first time.3
In the United Kingdom it was already understood that wireless
telegraphy was an open, and thus insecure, means of
communication. Indeed, Professor Oliver Lodge had confirmed this
point to the General Post Office (GPO) in 1903.4 The army too, had
realised that anyone with an appropriate receiver could listen to
such transmissions without much difficulty. Moreover, censorship
experience gained during the Boer War had taught the authorities
the advantages of controlling such emissions. In spite of the efforts
of a small number of wireless enthusiasts in the army, however,
the army in general continued to rely on cable and telegraph for
most of its communications.5 The Committee of Imperial Defence
(CID), formed after the Boer War to provide the government of the
3 Ibid.
4 Ibid.
5 Ibid., p.12.


28
day with the best available high level defence advice, took another
view. Lord Haldane, the Secretary of State for War from 1905 to
1912, shortly authorised the creation of a War Book containing
essential measures to be taken in the event of a major crisis or
war.
From this relatively simple but far-sighted and vital measure
sprang the idea of a formal Secret Service (MI5) and the
drawing-up, in advance, of a list of names of persons thought to be
suitably qualified for employment in intelligence and cypher duties.
The War Office attitude at the time discouraged the learning of
foreign languages. Eventually the commercial world was
approached for individuals who could speak foreign languages and
who might be employed on intelligence work. Several influential
firms, and others, responded and these included shipping lines, a
major bank and a telegraph company. In 1906 the army started to
think again about employing wireless as a major means of
communication. It was therefore somewhat fortunate that relevant
trials and experiments had been allowed to continue at centres
such as Aldershot and Chatham. At long last a new signal service
was formed and a Director of Telegraphs and Signalling approved.
It took the Army until 1913 before these changes were fully
implemented and Telegraph gave way to Signals, even so, the
cavalry was the only arm in the British Expeditionary Force (BEF)
equipped with wireless, until 1917. They made full use of it.
In 1909 Marconi was awarded the Nobel Prize for physics, but
this did not help him very much in the commercial sense. Progress
was slow and in the following year, exasperated by the delays and
political in-fighting occurring in London, his company proposed a
plan to link the Empire by wireless. His proposals using eighteen
high power stations were given further impetus by the knowledge
that Germany was embarking on a similar scheme to connect its


29
own colonies with Berlin.6 France too, had similar aspirations and
wished to establish communications between Paris and North
Africa. The CID was strongly in favour of an Empire wireless chain
and recommended such a link to the government. Because of
strong opposition to the Marconi Company, stemming from an
alleged stock exchange scandal, some ministers had bought shares
in the American Company, and it took until August 1913 before
the House of Commons approved final contracts for six wireless
stations, which would form a chain connecting Britain with
Australia. Marconi did not get his eighteen stations, but six were
better than none at all, or so he thought at the time. In the event,
the Marconi Company did not complete any of the six and when
the contract was cancelled, somewhat abruptly, it was awarded
£600,000 by way of compensation. Such was the antipathy,
however, displayed towards the Marconi Company because of the
share scandal, although not towards Marconi himself, that the
Empire had to wait until the autumn of 1927 for the installation of
a complete system of wireless communication.7
Naval intelligence then produced, at a subsequent
sub-committee meeting of the Committee of Imperial Defence, a
world-wide survey of British and foreign wireless stations in
considerable detail. This gave the CID the advantage of deciding, in
advance, which communications should be disrupted, intercepted
or left alone in time of war. At a second meeting of this important
sub-committee on 29 June 1914 the subject of intentional
interference or jamming was raised. Mr Wilkins the Treasury
6 Viscount Samuel, Memoirs (The Cressey Press, 1945), pp.74-77.
7 Frances Donaldson, The Marconi Scandal, p.243.


30
representative, ever mindful of the public purse, said:
it was for consideration how far it was worth expending
money on apparatus [i.e. wireless] that might be
rendered useless in wartime.8
In accordance with secret clauses contained in the War Book,
censorship of communications was imposed in August 1914. But
postal censorship had been overlooked and thus an appropriate
organisation had to be hurriedly introduced to discharge this
particular task.
Once trench warfare commenced in France in 1914, the
British Army found its beloved telegraph wires were soon destroyed
by German artillery fire. To stand any chance at all of passing
information to and from forward units, cables had to be buried
several feet underground and pigeons utilised as message carriers
on a massive scale.9 The few wireless sets that were available had
been allocated to the cavalry and these were used to good effect.
German transmissions were overheard with the aid of this
equipment and the intercepts passed to GHQ where they were
successfully analysed. Soon the British Army became proficient at
traffic analysis and, with the help of its newly developed technique
of Direction-Finding (DF), was able to identify many German
military units and formations and plot their positions and
subsequent movements. Needless to say the War Office was
delighted with this turn of events.10 Moreover, with the help of
8 Nigel West, GCHQ, pp.18-19.
9 Ibid., pp.28-29.
10 Ibid., p.30.


31
specialised wireless equipment German telephone conversations
were overheard. For similar reasons British conversations had to
be banned within 3,000 yards of the front line. This then was the
start of modern Signals Intelligence, or SIGINT, which not only
included interception of wireless signals but de-cryption of the
messages as well as a detailed analysis of the traffic itself. The
potential usefulness of SIGINT was not lost on the War Office,
which was then in the process of being reorganised by Kitchener. A
Director of Military Intelligence was re-introduced, and the BEF,
given its first Director, started to develop its own intelligence
organisation. Throughout the winter of 1916 the BEF took
advantage of the Germans' increased use of landlines by enlarging
and improving its SIGINT capability. A special unit analysed the
information obtained and recommended appropriate action. In
London, the War Office established units to study such intercepts,
to develop traffic analysis and to improve methods of decryption.11
Meanwhile, the Admiralty had made much progress with the
interception and de-cryption of German naval wireless signals.
They had created their own large and effective intelligence
organisation, which, with the aid of an efficient Direction Finding
service, was able at times to keep track of units of the German
surface fleet and U-boats and Zeppelins. Jamming of German naval
signals was also undertaken and some success achieved. Thus
allied ships and convoys could be routed around German U-boat or
surface ship locations, if these were known in advance. Then, if it
was both advantageous and possible to do so, an attempt could be
made to intercept and attack the German units. In this way eight
Zeppelins were destroyed in 1916 alone. Above all, perhaps, it was
11 Ibid., p.32.


32
the Admiralty's superb team of code-breakers in Room 40, which
enabled the allies to read much of Germany's wireless traffic.12
After the end of the war in 1918 the United Kingdom started to
disarm as quickly as possible. Careful plans had been drawn up to
prevent too many men being released too quickly thus causing
unemployment but, due to public clamour, these were abandoned
in favour of the principle of 'first in — first out'. Consequently,
within a year over four million men were demobilised. As the
demobilisation machinery gathered momentum, it became evident
that vital intelligence services and techniques could be lost in the
process. Consequently the War Cabinet, in 1919, decided to create
a Secret Service Committee to review existing arrangements. From
this came the important and far-reaching decision to establish a
Government Code and Cypher School (GC and CS — now GCHQ),
which came into existence on 1 November, 1919.13 The following
year a clause was inserted into the Official Secrets Act requiring all
cable companies operating from British territory to submit copies
of traffic, transmitted and received, to the government within ten
days.14 The tasks being passed to the Government Code and
Cipher School (GC & CS) were to study the ciphers used by other
governments and to advise on the security of national codes and
cyphers. From experience already gained, especially during World
War One, wireless traffic had proved to be a valuable source of
intelligence. Hence the origin of Signals Intelligence (SIGINT),
12 John Terraine, ‘The Substance of War’, in Hugh Cecil, and Peter H. Liddle, (eds.) Facing Armageddon, The First World War Experienced, (Leo Cooper, 1996), pp.6-7; Nigel West, GCHQ, pp.36-38.
13 F.H. Hinsley, British Intelligence in the Second World War, vol.1, p.20.
14 Nigel West, GCHQ, p.75.


33
which involves the study of communications systems, and
interception of such communications. Personnel for the new
organisation were recruited from staff formerly employed in Room
40 of the Admiralty and MI 1(b) of the War Office, the cost being
borne by the Foreign Office.
The War Office then decided to reorganise its SIGINT
arrangements and in August of 1920 formed the Royal Corps of
Signals. A military wireless communications chain was maintained,
with the overseas garrisons and intercepts acquired by elements of
the chain, or the garrisons themselves, being passed to GC and CS
for decryption and appropriate action. As a result of these
arrangements the Cabinet was furnished, inter alia, with
information disclosing Soviet involvement in the internal and
external affairs of the United Kingdom, including a subsidy paid to
the Daily Herald newspaper.15 In 1923 it was decided that the
head of the Secret Intelligence Service should become, in addition,
Director GC and CS. Although foreign cypher traffic was declining
at the time, the three armed services agreed with these changes,
albeit with some reservations. Nevertheless, a Naval Section was
added to GC & CS from 1924, an Army section from 1930 and, very
belatedly, the Air Section from 1936.16 Since its inception the
Army team had become involved with German air matters. This
parasitical arrangement suited the RAF as it saved manpower, but
with the surge in Luftwaffe traffic from 1935 onwards, the Army
15 Ibid., pp.76-77.
16 In the army and RAF, intelligence was then subordinated to operations, moreover RAF intelligence was not highly regarded in the 1920s and 1930s. Donald Cameron Watt, ‘British Intelligence and the Coming of the Second World War in Europe’, in Ernest R. May, (ed.), Knowing One's Enemies (Princeton, Princeton University Press, New Jersey, 1984), p.242, pp.256-260.


34
increasingly found it difficult to continue with the task, hence the
RAF presence from 1936.17 At the time all the service personnel
involved were employed on cryptanalytical work only. To provide
the necessary guidance and to establish priorities, GC & CS
established a Cryptography and Interception Committee in 1924;
but, since this met infrequently, a standing sub-committee had to
be formed four years later to co-ordinate all wireless interception.
This was the important Y Sub-Committee. The three services were
represented on both bodies and they retained control of the
personnel involved and their own interception stations. But they
could not have the latter everywhere: thus by the 1930s a system
had developed whereby the War Office concentrated, mainly but
not exclusively, on the Middle East, the Royal Navy on the Far
East, and the Royal Air Force, with its limited facilities, on the
United Kingdom. Even so, the War Office maintained a SIGINT
station at Devizes in the UK and the Home Office a station at 113,
Grove Park, Camberwell that concentrated on Soviet diplomatic
traffic.
2. The Royal Air Force 1919-1933
The year 1919 for the RAF was to mark the beginning, not the
end, of a struggle to maintain its existence as a separate and equal
armed service of the crown. The very man who helped bring the
RAF into existence, Lloyd George, raised the first hurdle to the
continuation of a third service. Re-elected in the 'Coupon Election'
of December 1918, the Prime Minister of the new government made
Churchill Secretary of State for War and Air, fully intending on the
grounds of economy, to dispense with the Air Ministry as a
17 Public Record Office (PRO) Government Code Headquarters HW 43/1, p.3.


35
separate department, as soon as he could conveniently do so. Lloyd
George then busied himself with the Peace Conference held in Paris
from January 1919. Later he was to change his mind about
disbanding the RAF, without any prejudice, however, towards
reducing government expenditure on defence. Thus for the moment
the RAF could expect to continue to exist as a separate service but
would still be subject to any necessary financial retrenchment.
Meanwhile, the first Chief of Air Staff, Hugh Trenchard, had
resigned his position over differences with Lord Rothermere, the
then Air Minister, but in the following year he had been persuaded
by Churchill to resume his former post.18 He returned to the Air
Ministry on 15 February 1919.19 He was going to need all his
faculties and powers of reasoning, if the infant RAF was to grow
and be accepted as an equal with the Royal Navy and Army.20
Trenchard was determined that the air force should continue
as a separate entity, no matter what its size, be administered as
economically as possible and, above all, be capable of rapid
expansion should the need ever arise. By 1920 the post-war boom
had turned into a slump and a year later into a depression. By this
time Lloyd George had introduced his 'Ten Years Rule', which
assumed that no major conflict would arise for the next ten years.
Conveniently, the rule was renewed annually and certainly had its
desired effect of tightening the Treasury grip on service
expenditure. Unfortunately for Trenchard this debilitating rule was
18 C. Webster and N. Frankland, The Strategic Air Offensive Against Germany, 4 vols. (HMSO, 1961), vol.1, pp.38-39.
19 Andrew Boyle, Trenchard (Collins, 1962), p.332.
20 Ibid., pp.343-344.


36
not rescinded until 1932.21 By then the years of minimal
expenditure on defence had adversely affected not only the state of
efficiency of all three services but also the nation's aircraft
industry. During a time of great financial stringency, therefore,
Trenchard not only had to convince the government of the day of
the necessity of maintaining a separate air force in peacetime, but
he also had to persuade the chiefs of the other services as well,
perhaps a harder task.
3. Hitler and Enigma
Germany had experimented with cryptographic devices in the
closing months of World War One, but little was heard of them
until 1926, when the German Navy began to be supplied with a
sophisticated military version of a machine called Enigma, the
Scherbius or civilian model of which was already in commercial
use.22 By the end of 1935 some 20,000 of these machines were
available for use by the three German services.23 Germany
continued to improve Enigma to such an extent that by the
outbreak of World War Two it considered the cypher safe from
decryption. Meanwhile, the Polish Cypher Bureau had become
interested in deciphering Enigma traffic as early as 1928, and had
acquired one of the commercial Scherbius machines.24
Subsequently, in 1931, the French acquired Enigma settings and
passed them for the first time to the Poles. A strong team of
mathematicians was employed on this complex task and resulted
21 Denis Richards, Royal Air Force 1939-1945, 3 vols. (HMSO, 1953), vol.1, p.18.
22 F.H. Hinsley, British Intelligence in the Second World War, vol.1, p.487.
23 Ronald Lewin, Ultra Goes to War (Hutchinson and Company, 1978), p.45.
24 Ibid.


37
in the Polish cypher teams starting to read Enigma messages. The
German Navy, however, decided to alter its Enigma in 1937 and
consequently the Polish teams were unable to continue to read the
navy traffic. The following year the indicating system used by the
German Army was altered, bringing Polish success with this
particular system to a halt.
In 1933 Adolf Hitler became Chancellor of Germany and
started to put in train a succession of events that ultimately would
lead to the opening of hostilities between that country and the
United Kingdom some six years later. As knowledge of the
expanding German armed forces, especially the German Air Force,
became known in London, disarmament gave way to re-armament
and it was at the beginning of this period that the Director of Air
Intelligence decided, in 1934, to increase the service's interception
capability and created a small wireless monitoring station at RAF
Waddington in Lincolnshire.25 Such was the influx of general traffic
intercepted, however, that a new department, AI 1(e), had to be
established in the Air Ministry in order to analyse it all.
In contravention of the terms contained in the Treaty of
Versailles, Hitler signed a decree in February 1935, formally
creating the Luftwaffe on the first of the following month.26 But
the German Air Force had already been formed and its existence
had been known for some time; indeed it had been considered to be
a potential menace to the United Kingdom the year before.27 Much
25 Nigel West, GCHQ, p.110.
26 David Irving, The Rise and Fall of the Luftwaffe, pp.44-46; Air Vice Marshal Tony Mason, Air Power: A Centennial Appraisal, p.47.
27 C. Webster and N. Frankland, The Strategic Air Offensive Against Germany, 1939-1945, vol.1, p.67.


38
low-grade wireless traffic started to be intercepted regularly from
1934 onwards and this helped in estimating the size and
dispositions of the German Air Force. Indeed, by this means some
sixty ground stations were identified along with 578 aircraft by
September of that year. High-grade information, however,
enciphered with the aid of the electro-magnetic Enigma machine,
remained unreadable, although some success was obtained at GC
and CS in 1937 when several of the older and less secure machines
were used during the Spanish civil war. Flowerdown and Fort
Bridgewoods, near Chatham, were the two intercept stations
involved.28 Even so, this limited success only seemed to confirm
that traffic encrypted with the aid of the newer versions of Enigma,
at the time only deployed inside the Reich, would be impenetrable,
provided the operators used the relevant procedures correctly.
To help find appropriate Enigma keys, the Polish bureau
started to develop a system of perforated sheets and introduced the
world's first electro-mechanical cryptographic bombe.29 To
complicate matters further, in 1939, the German Army's Cypher
office increased the number of Enigma plugboard sockets, thus
rendering the bombe unreliable as the main cryptographic tool.
Because of this situation, and following the British Cabinet's
decision to support Poland, the Polish cryptographers, in July
1939, decided to inform France and Great Britain of their success
with Enigma from 1933 to 1938, and that they could be successful
again if the new and enlarged perforated sheets could be produced
in quantity. Indeed, they actually built a number of Enigma
28 Nigel West, GCHQ, p.110.
29 F.H. Hinsley, British Intelligence in the Second World War, vol.1, p.492.


39
machines and presented one each to France and Great Britain.30 A
few days after Poland was invaded in September 1939, their
cryptographic team hurriedly moved to France where they waited
for the perforated sheets to arrive from the United Kingdom to
enable them to continue their work.
Meanwhile, the United Kingdom Government had decided that
Enigma, suitably modified by an additional British attachment,
known as Type-X, should be made available to the Royal Air Force
and the Army. If used correctly, this device made it impossible for
any intercepts to be deciphered. On hearing this news, the head of
GC & CS became so pessimistic that, in the event of a foreign
power adopting such a combination, he considered his
establishment would be rendered redundant. Nevertheless, the
Y Committee arranged for further intercept stations to be
constructed in order to be able to concentrate on German and
Italian diplomatic traffic. The Austrian Anschluss in March, 1938,
had a profound effect on the United Kingdom and France, not least
on their respective intelligence communities. Moreover, the
subsequent and disturbing events concerning the Sudetenland and
Czechoslovakia persuaded the Treasury to agree to an expansion of
GC & CS and thus, in 1939, very late in the day, a German section
was established and many additional linguists acquired from the
commercial world and universities. In addition, it was decided that
Bletchley Park, in Buckinghamshire, should be used as an
alternative to the London Broadway HQ.31 The then chief of the
Secret Intelligence Service, Admiral Sinclair, had purchased the
estate at Bletchley in 1938 with some forethought. Intercept
30 Michael Smith, Station X: The Codebreakers of Bletchley Park, p.19.
31 Gordon Welchman, The Hut Six Story (Allen Lane, 1982), p.9.


40
facilities, however, still remained somewhat slender as GC & CS
went on to a war footing on 1 August 1939, the Air Ministry still
depending on the small unit located at RAF Waddington.
Fortunately, and in accordance with Y Committee policy, the Air
Ministry had decided to prepare another site at Cheadle in
Staffordshire, and this, signals unit No 61, was destined to be
enlarged and become considerably more important as the war
progressed. Indeed, it was to become the Royal Air Force's pre
eminent Y Wireless Telegraphy intercept station.32
4. Radar and the Integrated Air Defence of the UK
Meanwhile, the international situation was deteriorating
rapidly. Moreover, there had been little significant improvement in
the United Kingdom's air defence arrangements since the end of
World War 1, although it is true that various plans had been drawn
up, such as the Steel-Bartholomew plan of 1923, which attempted
to integrate observer posts, anti-aircraft guns and fighter defence,
but relied on early warning being provided by sound locators, the
52 Squadron Scheme, and, with the re-emergence of the German
Air Force as a potential threat to London and other cities of the
United Kingdom, the Reorientation Scheme of 1935.33 Most of
these, however, were all variations of ideas extant in 1918. Some
improvements had been made with sound detection, and a few
detectors had actually been constructed out of concrete by the
Royal Engineers, for use by the Royal Air Force.34 Subsequent
trials with aircraft, however, had proved to be disappointing and
32 F.H. Hinsley, British Intelligence in the Second World War, vol.1, pp.14-15.
33 John R Bushby, Air Defence of Great Britain, pp.79, 81-82, 84-85.
34 Richard N. Scarth, Mirrors by the Sea (Hythe Civic Society, Hythe, Kent, 1995) plates 1-22.


41
tended to confirm current thinking that the bomber would always
get through to its target.35
Interest in air defence then began to gather pace, especially
within the Air Ministry itself. Action by the Air Ministry Director of
Scientific Research, H.E. Wimperis, resulted in Lord Londonderry,
the Secretary of State for Air from 9 November 1931, establishing a
special committee under the chairmanship of Sir Henry Tizard,
with Professors A.V. Hill and P.M.S. Blackett to help him. It met for
the first time in January 1935 and was known as the Committee
for the Scientific Survey of Air Defence. Meanwhile H.E. Wimperis,
who had designed the first course-setting bombsight for the Royal
Naval Air Service in 1917, enlisted the help of Watson Watt, the
Director of the National Physical Laboratory.36 The latter had been
a meteorologist and subsequently had devoted much time to
studying the detection and location of thunderstorms with the aid
of radio waves and equipment that included a cathode ray tube.
Watson Watt was therefore well aware of the reflective properties of
radio waves.37 With the help of his assistant, A.F. Wilkins, he
advised Wimperis that it might be possible to detect aircraft by
exploiting this phenomenon. From then on events moved swiftly.
Further pertinent details were quickly furnished to Watson Watt
who then submitted a remarkable document, which later came to
be known as the 'Radar Charter'.38 Members of the Committee
studied the charter on 21 February and were so impressed with the
author's grasp of the air defence problems, and the methods
35 Ibid., p.36.
36 Neville Jones, The Origins of Strategic Bombing (William Kimber, 1973), pp.20-21.
37 E.G. Bowen, Radar Days, p.7; John Bushby, Air Defence of Great Britain, pp.100-101.
38 Ibid., p.102.


42
proposed to overcome the manifold difficulties facing them, that
within a week the Secretary, A.P. Rowe, had not only informed the
then Air Member for Research and Development of this timely and
promising development, but gained his wholehearted support.39
The very same day the well-known and much written-about trial
was held near Daventry when a Heyford bomber reflected the short
waves emanating from a nearby BBC transmitter, the outcome
being clearly seen on a cathode-ray tube.40
Dowding was impressed with the results and set to work to
obtain public money for further research. With the backing of the
new Secretary of State for Air, Viscount Swinton, and the Air
Council, a sum of £10,000 was found surprisingly quickly, together
with a suitable research site, Orfordness, just 15 miles down the
coast from Aldeburgh in Suffolk. Soon, thanks largely to the
dedication of a small team of enthusiasts; the range of detection of
known aircraft was pushed out to a distance of forty miles, then
eighty and hundred miles.41 Various tests and trials followed,
leading to the problems connected with Direction-Finding being
largely overcome.42 By October 1935 the Research Station had
outgrown its facilities and moved to Bawdsey Manor, some fifteen
miles to the south, which offered better conditions for radar trials
and more secure surroundings. Such was the progress made that
shortly thereafter the Treasury agreed, as an interim measure, to
the necessary expenditure for a chain of five stations to be
39 Air Chief Marshal Sir Hugh Dowding, quoted in Denis Richard's, Royal Air Force 1939-1945, 3 vols., vol.1, p.404.
40 John Bushby, Air Defence of Great Britain, pp.104-105.
41 E.G. Bowen, Radar Days, p.16.
42 John Bushby, Air Defence of Great Britain, p.107.


43
established to cover the approaches to London.43 Consequently
contracts were placed, under great secrecy, with Metropolitan
Vickers for transmitters in the 6-15 metre range and A.C. Cossor
for the Receivers; the latter company being the largest
manufacturer of Cathode Ray tubes in the United Kingdom.44
Radar masts had now reached a height of over 200 feet and were to
go higher, but, in spite of possible construction problems, it was
still hoped that the new stations would be ready in time to
participate in the air defence exercise scheduled for that summer.
Due to delays in construction at the other sites, Bawdsey was the
only station fully to take part. The subsequent results were
disappointing, many aircraft not being detected or detected too
late. The Chief of Air Staff, Sir Edward Ellington, was sufficiently
far-seeing to decide that the project should, nonetheless, be
continued.45 It was to develop into the Chain Home (CH) and Chain
Home Low (CHL) early warning systems used so successfully
against German aircraft approaching the United Kingdom during
World War Two, especially in daylight during the Battle of Britain.46
As developments continued to take place at Bawdsey, thought
was given in the Air Ministry to deciding who was going to operate
the air-warning network and what method of recruitment and
training of the necessary personnel would be required. Operations
rooms were going to have to be manned in order to assess and
collate the acquired data and to operate the vital communications
system, which would enable fighter aircraft to be scrambled and
43 Denis Richards, Royal Air Force 1939-1945, vol.1, pp.23-25.
44 Reg Batt, The Radar Army (Robert Hale, 1991), p.16.
45 John Busby, Air Defence of Great Britain, pp.109-110.
46 M.M. Postan, D. Hay, J.D. Scott, Design and Development of Weapons, p.378.


44
subsequently guided to their respective targets. In 1936, Squadron
Leader R.G. Hart was the officer selected for this new task; in order
to be able to work closely with the scientists developing the radar
network, he chose Bawdsey as his training centre.47 While the
pertinent reporting procedures were being worked out, it became
apparent that it would be possible for two or more adjacent CH
stations inadvertently to report the same aircraft. In order to avoid
any confusion that might arise from such a situation, Hart
introduced the Filter Room where raw radar data could be
crosschecked and refined before being passed to Operations Rooms
for display and information purposes.48
With many of the major and most pressing problems of the
Chain Home (CH) system overcome, Tizard and Watson-Watt could
think more about future developments and address the difficulties
of installing radar equipment into the cockpits of night fighter and
other aircraft. Construction of ground stations had been difficult
enough even without having to take into consideration such factors
as power requirements, weight and size. In the air these
considerations of power, weight and size became paramount.
Fortunately, Tizard and Watson-Watt had already given some
thought to these problems and their views and ideas were passed
to the staff at Orford and Bawdsey Research Stations. What was
required was equipment small enough to be installed in a night
fighter, which would enable a pilot on his own to close from a range
of ten to fifteen miles down to about five miles.49 Dr E.G. Bowen
was eager and willing to head an airborne radar group, which, in
47 John Bushby, Air Defence of Great Britain, pp.115-116.
48 Ibid.
49 E.G. Bowen, Radar Days, pp.30-31.


45
the beginning, consisted of a staff of one. By the end of 1936 he
had successfully constructed an airborne radar receiver small
enough to be installed in a Handley Page Heyford aircraft from
nearby RAF Martlesham Heath, then the home of the Aeroplane
and Armament Experimental Establishment (AAEE).50 The work
was of critical importance and was eventually to lead to the first
use of Air Interception (AI) and Air to Surface Vessel (ASV) radar
equipment in aircraft. By the beginning of 1937, Dr E.G. Bowen
had achieved outstanding results with his airborne radar
transmitter and receiver, operating on a frequency of one-and-a
half metres, installed in an Avro Anson.51 At this stage Great
Britain was ahead of Germany in airborne radar, there simply
being no requirement at that time for Air Interception equipment in
a country with the most powerful air force in the world. The FuG
Lichtenstein BC AI radar, which was subsequently developed and
manufactured by Telefunken, entered service in 1942-43 and was
developed from the 1939 Lichtenstein B high-altitude radio
altimeter.52
Meanwhile, for the Royal Air Force, the whole concept of radar
was new, and secret, and only those who needed to know were
informed about its role in air defence and other uses. In 1936
Tizard suggested trials should be held to determine exactly how,
and how accurately, a controller would be able to direct an
intercepting fighter on to an enemy aircraft, using information
obtained from radar sources. As a result the Royal Air Force
subsequently held what came to be known as the 'Biggin Hill'
50 Tim Mason, British Flight Testing (Putnam, 1993), pp.42-43.
51 E.G. Bowen, Radar Days, pp.41-42.
52 Martin Streetly, Confound and Destroy, p.179.


46
experiment.53 It was from these extremely important trials, and
those that followed, that Fighter Command learned it could
dispense with wasteful, and generally inefficient, standing patrols,
requiring fighter aircraft to be constantly airborne, and instead to
rely on timely and accurate information from the Chain Home
network, augmented by information furnished by the Observer
Corps. For the first time radar and ground tracks were compared.54
In due course Controllers became proficient in the new technique
of directing fighter aircraft with the aid of recently introduced radio
telephony, and using filtered information displayed on a map
situated in front of them in the operation centre. With practice, it
became possible to estimate the course in degrees, which a fighter
pilot should steer in order to effect a successful interception. From
1937 to the outbreak of hostilities with Germany, the RAF
concentrated on improving air and ground radar, and in training
the personnel who were to operate the radar system.
In February 1940, J. Randall and H. Boot devised the world's
first magnetron at Birmingham University. This device produced a
pulsed output of over one-Kilowatt at ten centimetres, unheard of
figures at the time. Not only did the magnetron make it possible for
the British to introduce centimetric radar, but it also led to a
radical improvement in radar generally.55 Quite early in 1940 Sir
Henry Tizard suggested that British secrets should be disclosed to
the USA in return for technical and production assistance. Both
53 Ibid., pp.117-119.
54 Ibid.
55 Reg Batt, The Radar Army, p.96; Air Vice Marshal R.A. Mason, Air Power: An Overview of Roles, pp.18-19.


47
governments agreed by late July to the visit by Tizard.56
Consequently, towards the end of August 1940, Sir Henry led a
Mission to Canada and the USA, in the course of which British
secrets such as the jet engine, radar in its many forms and the
unique resonant magnetron were disclosed.57 Indeed, the hope was
to invoke the technical and productive resources of the whole North
American continent. In this way, over a million magnetrons of every
type came to be made by US companies in the United Kingdom, or
in the USA, which were subsequently incorporated in hundreds of
thousands of allied radar sets, including those used by the Royal
Air Force.
The Observer Corps was not a new organisation, having come
into existence as a result of the knowledge and experience gained
during the German air raids on London during World War One. It
was to make a big contribution in World War Two. A Major
General, E.B. Ashmore, had been made responsible for organising
the air and ground defences and for extending the system beyond
the Metropolitan area. The observer network comprised a number
of posts linked by telephone to a control room. These were manned
at first by troops, and later police, who used a common reporting
code based on a gridded map. At the end of the war in 1918,
Ashmore proposed the formation of a peacetime air-defence
network composed of aircraft, guns, searchlights and observers
enrolled as special constables, all placed under one commander.
The Committee of Imperial Defence subsequently approved the
56 E.G. Bowen, Radar Days, pp.150-151.
57 Colin Latham and Anne Stobbs, Pioneers of Radar, pp.4-5.


48
scheme and the corps was officially approved in October 1925.58
Subsequent air exercises proved the indispensable value of the
Observer Corps and brought closer links with the Royal Air Force,
resulting in the appointment of Air Commodore E.A.D. Masterman
RAF (Ret'd) as the first Commandant in 1929.59 As radar was
introduced and integrated into the air-defence arrangements from
1936 onwards, visual reporting of enemy and friendly aircraft,
especially when flown at low level or overland, was given as much
prominence as ever. King George VI was to award the prefix 'Royal'
to the Observer Corps in 1941.60
5. Telecommunications Research Establishment (TRE) and the Start of Radio Countermeasures
It is noteworthy that up until the first half of 1936, personnel
working at Bawdsey had been employed by the National Physical
Laboratory; but on 1st August of that year, responsibility for the
Bawdsey Research Station (BRS) passed to the Air Ministry, thus
enabling Squadron Leader R.G. Hart to start his radar training
courses at that location. Watson Watt moved up to the Air
Ministry in 1938 to become Director of Communications
Development (DCD), being replaced at Bawdsey by the former
Secretary to the Tizard Committee, A.P. Rowe. In accordance with a
plan devised by Watson Watt, BRS moved to Dundee University in
Scotland in September, 1939, the airborne side going to Perth. A.P.
Rowe was a capable, scientific civil servant; but moving there was
an unwise decision, the accommodation being unsuitable, as it was
58 Directorate of Public Relations (RAF) Chronology: 50th Anniversary of the Royal Air Force (MOD, 1968), p.10.
59 Derek Wood, Attack Warning Red, p.29.
60 Directorate of Public Relations (RAF) Chronology, p.17.


49
at Perth. Taffy Bowen placed the blame for this state of affairs
firmly on the shoulders of Watson Watt and A.P. Rowe.61 In spite of
the location, the organisation was still expanding and one of the
several recruits at the time to the airborne division was a young
Bernard Lovell. The title Bawdsey Research Station was obviously
unsuitable for Dundee, and was changed accordingly to Air
Ministry Research Establishment (AMRE). After two months the
airborne side, complete with aircraft and forty odd personnel of D
Flight AA&EE, moved to RAF St Athan. On the face of it, St Athan
should have been ideal, being a large station and well away from
the East and South coasts: but it was a busy technical training
unit with limited resources. Since St Athan was an unsuitable
place to conduct research, most of the work here involved fitting AI
into Blenheims for Fighter Command, and ASV mainly into
Hudsons of Coastal Command. However, in May 1940, while
momentous events were taking place on the Continent, both
components of AMRE were moved to yet another location, Swanage
in Dorset, to a specially prepared, but ill-equipped site on the
coast, vulnerable to German air attack and assault from the sea.62
However, AMRE now became the Telecommunications
Research Centre (TRE), with D Flight, originally from Martlesham,
being absorbed into TRE's airborne division, being based at
Christchurch aerodrome. It was here at Worth Matravers, in
August 1940, that a Radio Countermeasure Group (RCM) headed
by Dr Robert Cockburn was created. The RCM Division was
developed from this. At the time, most of TRE's research was
directed towards protecting the United Kingdom, and its
61 E.G. Bowen, Radar Days, pp.84-87.
62 Ibid., pp.137-138; PRO Avia 7/601; Pro Avia 7/602; Pro Avia 7/603.


50
manufacturing industry, from the attentions of the Luftwaffe. Much
effort, therefore, had to be given to improvements and
strengthening of the RAF's night fighter defences, especially in the
further development of the first air interception radar (AI). In 1941,
TRE proposed that some form of radio countermeasure might be
used to support offensive air operations. The idea was a novel one;
Bomber Command, the sole means of carrying the war to the
German homeland at the time, rejected it out of hand, believing
that their existing methods of navigation were adequate and that
Radio silence had to be maintained at all costs, if the position of
their aircraft was not to be disclosed to the Luftwaffe. Bomber
Command was over-confident in its ability to deliver the bomber
offensive. Fighter Command, however, had no such objections. On
22 June 1941, Germany attacked Russia and, in doing so, had to
deploy much of the Luftwaffe away from the West in order to
support its operations in the Mediterranean and the East. This in
turn freed TRE to come to the assistance of Bomber Command
which, because of rising casualties, poor navigation and bombing
inaccuracy, was now more disposed towards the use of radio and
radar aids. But TRE did not always enjoy the highest of priorities
and it took the discerning Lord Cherwell to realise that, once
Churchill had been persuaded to back priority development of
scientific navigation and bombing aids, additional measures were
necessary. This resulted in the appointment of Sir Robert Renwick
who, in addition to his other responsibilities, was required to
coordinate the research, development and production of all such
devices for aircraft.63
63 PRO Air 20/8953, p.5.


51
6. Fighter and Bomber Commands
The Royal Air Force functional Commands were created in
1936 and, in July of that year, Sir Hugh Dowding was appointed
the first Air Officer Commanding-in-Chief of Fighter Command.64
He had been Air Member for Supply and Research since September
1930 and, was, briefly, Air Member for Research and Development,
before taking up what was to prove his most formidable task as a
serving officer. He was thus in an ideal position to watch the
growth of radar, encourage its development and promote its
deployment. Under his leadership Fighter Command became an
efficient and fully integrated air defence organisation, complete
with radar early warning, fighters, communications, barrage
balloons, observers and anti-aircraft guns; it was thus well placed
to protect the United Kingdom when it was most needed. With
regard to Bomber Command, it was a different story. For the same
economic reasons as those which made the politicians favour the
production of less costly fighter aircraft, bomber production was
less favoured than that of smaller and lighter aircraft.
Consequently, Air Staff plans for heavier aircraft were not always
approved and manufacture was either delayed or scaled down. As a
consequence of financial restraints and the Air Ministry's belief
that the bomber would always get through, there was little
incentive for research and development. Consequently, Bomber
Command was neither well trained in navigational and bombing
techniques, nor equipped with suitable aircraft. It was thus
incapable in 1939 of bombing targets accurately in Germany and
inflicting any meaningful damage on German industry.
64 Denis Richards, Royal Air Force 1939-1945, vol.1, p.404.


52
Bomber Command's first Air Officer Commanding-in-Chief
was Air Chief Marshal Sir John M. Steel, GCB, KBE, CMG, but his
tenure was destined to last only a little over a year. Sir Edgar
Ludlow-Hewitt replaced him at the time of the Munich crisis. The
Command was not only short of heavy bombers but of aircrew as
well. Moreover, crews were unable to navigate accurately, especially
by night. In the circumstances the recently introduced policy of
only attacking military targets, in the event of an outbreak of war,
was generally welcomed by the AOC-in-C. Not surprisingly, the Air
Ministry was now allowed by the government to order as many
aircraft as could be produced and, as fighters were quicker and
cheaper to manufacture, the benefits of this decision fell to Fighter
Command. The Air Ministry was well aware of the danger of
expanding the force too quickly, but time was short. Due to years
of disarmament and financial stringency, half of the aircraft of
Bomber Command lacked the range to attack Germany from bases
in the United Kingdom.65 Given a numerically superior German Air
Force, Bomber Command thus could do little else but delay the
onset of a policy involving all-out attack for as long as possible.66
Even the Chief of Air Staff, Sir Cyril Newall, was compelled to
acknowledge on the outbreak of war that Bomber Command was
too weak to launch an offensive against Germany.
7. Development of Radar in Germany
A German national, Christian Hulsmeyer, first patented a
radar device in 1904.67 It was not very efficient and some twenty
65 Richard Overy, Why the Allies Won, p.107.
66 C. Webster and N. Frankland, The Strategic Air Offensive Against Germany 1939-1945, vol.1, pp.100-101.
67 David Pritchard, The Radar War, p.14.


53
five years were to elapse before the necessary technology became
available for the principles involved to be incorporated into a
practical device. A Professor Braun had built a cathode ray tube as
early as 1897, and in 1924 pulsed wireless signals were utilised to
find ranges of objects. These advances were followed by the work of
Dr Yagi of Japan who in 1929 showed how wireless signals could
be transmitted for the very first time in fine beams employing
directional aerials. By 1933, Dr R. Kuhnold, of the German Navy's
Research Department, had been experimenting with radar; a year
later the Gema Company began constructing his detection devices.
Subsequently improvements to prototypes led him to employ
pulsed transmissions operating on 600 Mcs. The upshot was that
in 1935 ships could be detected at five miles and coastlines at
twelve, the device becoming known in Germany as Dezimeter
Telegraphie or DT-Gerät. In 1936 the operating frequency was
altered to 150 Mcs, with the result that aircraft could be detected
at ranges up to thirty miles. Eventually, Dr Kuhnold produced the
Freya early warning radar initially operating on 125 Mcs, which by
the end of 1936 could detect aircraft at a range of fifty miles.68 By
the summer of 1938 Freya was ordered first by the German Navy,
who took possession of their initial equipments in 1938. It was
then ordered by the Air Force. Good though Freya was as an early
warning device, the German Navy wanted an accurate gun-ranging
device. The Gema Company obliged by producing Seektakt, an
early model of which, working on a frequency of 375 Mcs, gave a
range of nine miles. By the summer of 1938 it was fitted to the
pocket battleship Graf Spee, and the Scharnhorst and Gneisenau by
November 1939. By contrast, at the beginning of the war only two
68 Ibid., p.49.


54
ships of the Royal Navy possessed radar, both Type 79 air-warning
sets.69 The Telefunken Company too, was interested in radar and
entered the field in 1936. Perhaps they had spotted a niche in the
market, for Freya lacked a height-finding capability. The result was
the highly mobile and accurate Wurzburg set which arrived in
1938. It could plot aircraft to within very fine limits at ranges up to
25 miles, operating on 560 Mcs, and was a very accurate device
indeed. At the same time Telefunken designed and built a small
airborne radar set, trials beginning in the summer of 1939 with
Ju 52 aircraft. Some of this information found its way back to
British Intelligence, but was largely dismissed on the grounds that,
because radar was a British invention, it was unlikely that
Germany could have developed the device so quickly.
8. Development of Radio in Germany
It was Erhard Milch, who shortly after becoming a Director of
Lufthansa in 1925, insisted on blind-flying training for his pilots
and asked German industry to provide the necessary
instruments.70 With this in mind it should not come as any
surprise to find that use of wireless aids to assist with navigation
was strongly advocated in Germany before World War Two.
Consequently, during the 1930s some twenty-four medium
frequency beacons were established; by September 1940, this
figure had risen to thirty-eight. These devices transmitted a call
sign followed by a twenty-second continuous note, enabling the
crew of the aircraft to obtain a bearing on the known location of the
beacon. Frequencies employed were in the range 176-580 Kcs, and
69 Len Deighton, Blitzkrieg, p.118.
70 David Irving, The Rise and Fall of the Luftwaffe, p.19.


55
the information obtained was used to confirm turning points, and
for homing, as well as general navigation.71
As early as 1933, the German wireless industry had
anticipated the future needs of a German Air Force by starting to
experiment with various forms of wireless aids which could
possibly be used for navigation and bombing purposes, even when
aircraft were supporting the German Army in the field.72 Indeed,
the Lorenz Company evolved a short-range airfield approach
system, employing very high interference-free frequencies (VHF).
Morse dots were heard to one side of the beam, and dashes to the
other; a steady note was heard when the beam was being followed.
Unlike modern equipment, no glide path facility was fitted, but in
the horizontal plane the beam was very accurate. In the United
Kingdom the Lorenz system was known at first as Standard Blind
Approach, and, later, as Standard Beam Approach. Lufthansa, the
Luftwaffe, the Royal Air Force and others adopted this 'blind'
landing device. It was believed at the time that these VHF
transmissions were limited to a range of about 20-30 miles for an
aircraft flying at about 2000 feet. (See Figure 1). Unknown to the
Royal Air Force, the Germans had discovered that with a powerful
VHF transmitter, coupled with an appropriate aerial array, signals
could be received at distances of up to 250 miles by aircraft flying
at 20,000 feet. With the aid of a second transmitter, located so as
to provide an intersection over the target, Lorenz had developed a
blind bombing device for the Luftwaffe, operating on 30.0 to 33.3
megacycles (Mcs), with beam widths of 0.33 degrees. This device
was given the name Knickebein. Little additional training was
71 F.H. Hinsley, British Intelligence in the Second World War, vol.1, pp.550-551.
72 Ken Wakefield, Pfadfinder, pp.4-5.


56
R.V. Jones
Figure 1
Diagram explaining principle of Lorenz Beam which, at the time
was thought to have a maximum range of some fifty miles


57
required by German aircrew as the receiver was incorporated in the
standard airborne beam approach equipment FuBl 1, and could
therefore be used by the crews of all Luftwaffe bomber aircraft
fitted with standard blind approach equipment.73 (See Figure 2)
While Telefunken GmbH was manufacturing Knickebein,
Lorenz commenced work on another VHF blind bombing system,
X-Verfahren. It was developed at Rechlin by a team led by Dr Hans
Plendl and comprised a complex multi-beam device using
66.0-77.0 Mcs. The track to be followed was one of fourteen,
usually seventh from the left, and was adjusted for crosswind over
the target; the others were false or decoy beams. Lorenz,
Telefunken and Siemens all contributed to the development of
X-Gerät or Airborne Equipment. Dot-dash keying facilities were
employed akin to those of Knickebein, but the beams were much
narrower, being only 1 Km wide (1,100x) at a range of 100 Kms (62
miles). The beams, however, were made up of 180 directional
signals per minute and required an analyser to decode them,
making interference unlikely, even if the beam in use could be
identified. Until 1941, the device included two Telefunken Anna
VHF receivers, two associated aerials with separate masts, two
Siemens signal analysers, an inverter, a power distribution panel,
two course meters and an automatic bomb-releasing clock, or
X clock. To carry out a blind bombing attack required an
operational aircraft, normally a Heinkel HE 111, complete with this
equipment and a specially trained crew. In 1938 therefore the
Luftwaffe had a second blind bombing device, albeit at the time
fitted into Junkers Ju 52/3m. By 1939 it had the potential to form
and utilise a pathfinding force with its latest equipment. Not
73 Ibid. pp.5-9.


58
AIR 41/46
Figure 2
Copy of Knickebein Document
Captured in July 1940


59
content with Knickebein and X-Verfahren, Germany decided to
develop another precision blind bombing system. This was
Y-Verfahren, devised by Dr Plendl at the Rechlin Test Centre; it
was technically more advanced than the other two devices, and it
was also considerably more accurate. It employed a single VHF
beam for guidance to the target, the aircraft's position being
determined electronically by a second transmitter, employing range
or distance equipment. Using Y-Verfahren, or Benito, it was
necessary for a ground controller to pass a bomb release signal
when the aircraft was over the selected target.74 (See Figure 3)
So German radar developed completely independently of the British
and for different reasons. Germany wanted Radar for coastal
defence and for their warships, together with an early warning
radar and an accurate height-finding device with which to control
guns and searchlights. Britain, on the other hand, wanted a Chain
Home and Chain Home Low system for fighter defence. In the
United Kingdom these requirements were given a high priority. In
general German equipment was better designed and produced. The
architects of the Luftwaffe always intended that it should be a
balanced air force, consisting of fighters, bombers and transport
aircraft, capable of supporting the German army. By 1936, Dornier
had already built prototypes of the Do 19 and Junkers the Ju 89.
Goering, however, scrapped both aircraft and all four-engined
aircraft in 1937.75 By the time this mistake was recognised a year
later, and the He 177 was ordered as a substitute, with the proviso
that it should be capable of dive-bombing, it was too late to affect
74 Ibid., pp.49-51.
75 David Irving, The Rise and Fall of the Luftwaffe, pp.45, 54-55, 66.


60
AIR 41/46
Figure 3
Diagram of Benito System


61
the strategic bombing of the United Kingdom.76 By default
therefore, the Battle of Britain and the subsequent night-time Blitz,
had to be conducted by the Luftwaffe with what, essentially, was a
tactical air force. Now that the historical development of radar has
been discussed as essential background to the thesis, I will
investigate just exactly how the British discovered the German
beacons and beams and establish what they did about it.
76 Ibid., p.66.


62
CHAPTER TWO: GERMAN BEAMS AND BEACONS
1. KGr 100, X-Verfahren and Knickebein
In Germany in March 1939, selected aircrews were receiving
training in the use of the X-Verfahren system. This was a wireless
navigation and blind bombing beam. Heinkel (He) 111 aircraft were
employed and practice bombs were being dropped on targets, with
the aid of X-Gerät equipment, from heights as high as 28,000 to
30,000 feet, often with accurate results. The unit concerned, LnAbt
100, made sufficiently good progress for it to be declared
operational by 1 September 1939, in time for the attack on
Poland.1 X-Gerät was thus used operationally for the first time
against military targets by day and by night, the crews concerned
gaining valuable experience with this device. Soon after the
outbreak of hostilities, the Luftwaffe was conducting
reconnaissance and limited anti-shipping strikes over the North
Sea and against elements of the British fleet based on the Firth of
Forth. On 18 November 1939, the Luftwaffe unit concerned became
a bomber wing, KGr 100, and when the tempo of these operations
was increased, the opportunity was taken to hold Knickebein (a
more elementary wireless navigation and blind bombing beam) and
X-Verfahren trials over France and the East Coast of Britain in
order to prepare for the forthcoming bombing campaign. To
support these activities the existing M/F beacons and Knickebein
transmitters were augmented by appropriate X-Verfahren
transmitters positioned near Baden Baden, Krefeld and on the
island of Borkum.
1 Ian Kershaw, The ‘Hitler Myth’: Image and Reality in the Third Reich (Clarendon Press, Oxford, 1987); Ken Wakefield, Pfadfinder, p.16.


63
2. Denmark, Norway, the Blitzkrieg and Dunkirk
On the earlier advice of Admiral Raeder, Hitler authorised
preparation of a detailed plan for the seizure of Norway on 17
January 1940.2 Warnings of Operation Weser Rubung had been
received in Whitehall but largely ignored and thus the invasion of
Denmark and Norway on 9 April achieved total surprise.3 KGr 100
took part in this operation but, somewhat surprisingly, without its
X-Gerät equipment.4 Just over a month later German forces
attacked in the West, frequently employing Blitzkrieg tactics, with
the result that Belgium, Holland, Luxembourg and France soon fell
to the combined effects of the German Army and Air Force.5 The
British Expeditionary Force (BEF) was forced to retreat and leave
most of its heavy guns and transport behind, together with two
Type-X cipher machines, without, fortunately for the British, their
all-important cipher wheels. By early June 1940, less than one
month from the start of the German assault, much of the BEF had
been evacuated from the continent of Europe though at
considerable cost in aircraft, especially Hurricane fighters, ships,
and men.6
3. Knickebein Revealed
Shortly after the catastrophe at Dunkirk in May and June
1940 GC&CS, at its new headquarters at Bletchley Park
successfully decoded an Enigma message referring to a radio beam
2 Ibid., p.20.
3 F.H. Hinsley, British Intelligence in the Second World War, vol.1, pp.115-117.
4 Ken Wakefield, Pfadfinder, pp.21-22.
5 Ian Kershaw, The ‘Hitler Myth’: Image and reality in the Third Reich, p.152.
6 Martin Gilbert, Winston S. Churchill, vol.6, pp.406-407.


64
situated near Kleves, the nearest part of Germany to the United
Kingdom.7 To Dr R.V. Jones, the brilliant scientist of RAF Scientific
Intelligence at the Air Ministry, this news, together with that
obtained from the interrogation of prisoners of war and
examination of German radio equipment taken from crashed
aircraft, confirmed the existence of a system of narrow radio beams
used for navigation and bombing. Moreover, the disclosures in
1939 contained in the Oslo Report of, inter alia, a description of a
radar early warning system and the finding of a radio rangefinder
aerial with an operating frequency of 57 or 114 cms on the Graf
Spee by L.H. Bainbridge-Bell, strongly suggested to Dr Jones that
the Germans were fully capable of producing radar - if they did not
already possess it. His opinion, however, was not universally
accepted in London.8 In accordance with thinking at the time,
doubt was also expressed that radio waves transmitted from
Germany in the 30 megacycle band, and similar to those used for
the Lorenz landing beam, could be employed for such purposes
over the United Kingdom, especially as the maximum range of
these radio beams was considered to be around 50 miles, at most.9
Sir Henry Tizard was among those who expressed the view that the
beams could not provide pinpoint accuracy over the ranges
envisaged and, because of this, he considered that far too much
7 R.V. Jones, Most Secret War, pp.92-94.
8 PRO Air 20/1622 ASIR Report No.5 dd. 23 May 40; F.H. Hinsley, British Intelligence in the Second World War, vol.1, pp.508-512. The Oslo Report sent anonymously to the British Naval Attaché in Oslo in November 1939 was one of the most remarkable intelligence reports of the entire war. It disclosed, inter alia, the existence of the new German bomber aircraft the Ju88, and its production program, the presence of the secret Luftwaffe laboratories and test range at Rechlin, and that German radar provided early warning of the RAF attack on Wilhelmshaven, 4-5 September 1939.
9 Ronald W.Clark, Tizard, (Methuen and Company Limited, 1965), p.230.


65
excitement was being generated about the whole affair.10
Nevertheless, since this frequency band was one utilised by
German blind landing receivers, installed in Luftwaffe bomber
aircraft, the system could be used routinely by aircrew of the
bomber force.11 It was known as Knickebein (or Crooked Leg) to the
Luftwaffe and by the code name Headache to those involved with
such matters in the United Kingdom.12
In spite of the fact that the Standard Telephone Company
owned the rights to the Lorenz system, the pre-war RAF possessed
nothing like it.13 Although the Blind Approach Training and
Development Unit was formed at Boscombe Down on 29 September
1939, Blind Approach Training was only introduced to the service
in general in January, 1940, some five months after the outbreak
of war.14 Moreover, the necessary instrumentation for operational
aircraft was not fitted until the following December.15 On 15 June,
1940, with a defeated Army at home, almost bereft of its heavy
guns and equipment, and an invasion expected daily, a meeting
was held at the Air Ministry under the chairmanship of Air Marshal
Sir Philip Joubert, who had been appointed the day before by the
Secretary of State, Sir Archibald Sinclair, to take charge of the
investigation into the German beams.16 At this meeting it was
decided that there was sufficient evidence of beam activity to take
10 Ibid.
11 PRO Air 41/46 App.“A”.
12 PRO Avia 7/779; PRO Avia 26/407.
13 John Ray, The Night Blitz 1940-1941, p.124.
14 Norman Longmate, The Bombers (Hutchinson, Norwich, 1983), p.68.
15 Tim Mason, The Secret Years, p.310; Directorate of Public Relations (RAF), Chronology (MOD, 1963), p.16.
16 R.V. Jones, Most Secret War, pp.95-96.


66
immediate action. It was not long in coming. The following
afternoon, at a further meeting, the Director of Signals was
authorised to form a flight of aircraft for the purpose of finding the
beams. Other decisions were: Watson Watt and R.V. Jones to
inquire into the possibility of placing receivers on Chain Home
radar towers and Group Captain L.F. Blandy, a Deputy Director of
Signals and head of the RAF 'Y' Service, to evolve a method of
jamming the Knickebein transmissions.17 Such jamming required
the production in the output of the enemy receiver, of sufficient
energy to prevent recognition of the wanted signal.18
Under the threat of German airborne and seaborne landings,
Blandy quickly created a section in the Air Ministry to deal with the
jamming of German wireless beams and placed Wing Commander
E.B. Addison, a signals specialist, in charge of such activities.19
Accordingly, American Hallicrafter receivers were purchased at an
appropriate radio retailer, as none were available from RAF
sources, and placed on five of the Chain Home's radar masts, by
now three hundred-feet high, in an attempt to intercept the beams
from the ground.20 (See Figure 4) Subsequently, the listening
watches were regularised and placed on a formal basis; and later,
when it was established that the current scientific theory was
invalid, and that the German beams could indeed be used over the
United Kingdom for the purposes envisaged, the network was
extended inland. It was also decided to re-form the recently
disbanded Blind Approach Training and Development Unit (the
17 Norman Longmate, The Bombers, p.68; PRO Air 20/8953, p.38.
18 PRO Air 26/280; PRO Air 26/580; PRO Avia 7/779.
19 PRO Air 26/280; PRO Air 26/580.
20 R.V. Jones, Most Secret War, p.97.


67
Brian James
Figure 4
Ultra High Frequency Radio Receiving Equipment
Hallicrafters S 36


68
only one) as the Wireless Intelligence Development Unit (WIDU) at
Boscombe Down, near Salisbury, with a detachment at RAF Wyton,
in Huntingdonshire.21 The aircraft establishment of the new unit
was increased to eight Ansons and three Whitleys, with a
corresponding increase in air and ground crews.22 RAF pilots
experienced in beam flying made up the nucleus of the new unit,
which was commanded by Wing Commander R.S. Blucke.23
Among the first aircraft made available for the air investigation was
an Avro Anson, fitted with Lorenz blind landing apparatus. In an
attempt to hear beam signals from the ground, a van was obtained
and fitted with a United States Hallicrafter radio receiver and, for
crude jamming purposes, a hospital diathermy jammer set tuned
to 31.5 Mcs. The remainder of the month was spent searching for
proof of Knickebein activity and deciding on the best policy for
interfering with the beams effectively, when found.24 Two days
later, further information from intelligence sources confirmed the
position of the Knickebein transmitters in Germany at Kleves and
at Bredstedt.25
On the third day of the air search, during the evening of the
21 June, 1940, the beams were found on the expected frequencies
of 31.5 and 30.0 megacycles, respectively, by an Anson aircraft of
the newly formed WIDU, captained by H.E. Bufton.26 (See Figure 5)
Three nights later, one of the tower listening stations reported
21 For a good description of life at Boscombe Down at the time, see Tim Mason, The Secret Years.
22 Michael Cumming, Beam Bombers, p.15.
23 PRO Air 26/580.
24 PRO Air 20/1623; PRO Air 20/1626; PRO Air 41/46 and App.“A”.
25 PRO Air 41/46, p.4.
26 PRO Air 20/1624.


69
R.V. Jones
Figure 5
Knickebein Beams found evening 21st June, 1940


70
hearing beam type signals on similar frequencies. With an
elementary listening system in place, countermeasures could now
start to be devised. While the listening facilities were being
organised, emergency action was taken against the Knickebein
beam itself. A number of electro-medical (diathermy) sets were
borrowed from local hospitals and used as crude jammers, two of
the appliances being modified to cover 30 mcs, but without keying
facilities. They were placed in vehicles, containing receivers for
intercepting beam signals and sent Wyton in Huntington and to
Boscombe Down in Wiltshire, for dispatch to any specified target
area.27 Tests by No 109 Squadron, however, indicated that the
selected sets were unlikely to be successful. Further apparatus was
thus obtained from similar sources, twelve of the most suitable
being altered for the purpose and provided with audio modulation.
They were deployed at police stations on the East and South
Coasts and controlled from H.Q. Fighter Command.28 A few days
later Intelligence confirmed the existence of Freya, a German Early
Warning radar, and the X-Verfahren (Wotan I) and the more
advanced Y-Verfahren (Wotan II) navigation and bombing devices,
which came as a shock in London. About the same time,
intelligence was received about a new Knickebein transmitter to be
set up in the Cherbourg and Brest area of France. The conclusion
drawn was that the Germans clearly intended to make full use of
all these systems in order to expedite the forthcoming bombing
campaign against the United Kingdom. Hence the rush by the
Germans to erect appropriate aerials in northwest France and
Holland, as quickly as possible. As mentioned earlier, there had
been insufficient time for Luftwaffe signals personnel to erect
27 A.I.1 (e) Reports 26 June 1940 and 28 June 1940, quoted in PRO Air 41/46, pp.4-5.
28 Ibid.


71
Knickebein equipment during the rapid Polish campaign, however,
the smaller and more mobile X-Verfahren was deployed and used
operationally.
Before appropriate jamming equipment could be designed and
produced, it was essential to know as much as possible about how
Knickebein worked. Information from prisoners of war, maps from
aircraft that had crashed in the United Kingdom and Enigma
decrypts provided valuable clues about Knickebein. It was thus
believed at the time that the early Knickebein was capable of being
directed to a specific location over the United Kingdom, within an
accuracy of 0.1 degree, thus enabling the crew of an aircraft to find
a target in adverse weather conditions by day or night. The
airborne receiver was incorporated in the standard Lorenz landing
beam equipment, E.Bl.1, or Empfänger Blind 1. The early mark of
the ground transmitter comprised two aerial arrays set at an angle
of 165 degrees, each array consisting of two stacks of eight vertical,
centre-fed full-wave wire aerials, complete with reflectors, operating
on the fixed frequencies of 30 and 31.5 megacycles. The aerials
were attached to a framework 315ft by 100ft that could be rotated
in the direction of the target with the aid of wheels. Interlocked
dots and dashes were then transmitted by this system on the audio
frequency of 1150 cycles per second as complementary signals.
Along the three-degree width equi-signal, a continuous note could
be heard in a receiver, while dots could be received on one side and
dashes to the other. Discrimination in determining the continuous
note gave the effect of a beam. Morse keying occurred at a rate of
60 characters per minute and the ratio between the duration of the
dot and the dash was 1/7. As was to be expected with VHF
transmissions, the range of Knickebein varied with the height of


72
the aircraft.29 By the use of two Knickebein transmitters it was
possible to arrange for the beams to meet over the intended target.
Indeed, intelligence had already suggested that these were
positioned at Bredstedt, Husum and Kleve. The Germans
subsequently installed a number of Knickebein transmitters along
the coast of the Continent, adjacent to the British Isles, thereby
reducing the height at which their aircraft would otherwise have to
operate, when attacking industrial and other targets situated in the
United Kingdom.30 (See Figure 6)
4. Luftwaffe M/F Beacons and RAF Countermeasures
In July 1940, the usually accepted view held in the United
Kingdom was that medium frequencies were not suitable for
accurate navigation purposes at night, because of poor propagation
leading to inaccurate bearings. Nevertheless, a further decision was
taken that month to prevent the Luftwaffe from using the well
known pre-war network of medium frequency radio beacons, which
was now being extended to cover the occupied countries and the
United Kingdom. By March, 1940, some forty-six were in operation
and Sir Hugh Dowding, AOC-in-C Fighter Command, had good
reason to believe that the Luftwaffe could be using the beacons as
an aid to navigate accurately to targets situated in the United
Kingdom.31 In order to put a stop to this, a system of masking
German beacons was introduced.32 The Radio Branch of the GPO
had earlier devised this masking, or Meacon, system for a slightly
29 Alfred Price, Instruments of Darkness, p.23.
30 PRO Air 41/46 App.“A”.
31 PRO Air 20/8963, Enclosures 4A and 5A.
32 PRO Air 41/46, p.8.


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74
different purpose.33 Frequencies could be altered quickly, the
transmitters being designed to re-radiate the German beacon
signals thus making it difficult, or impossible, for these to be used
for accurate Direction Finding and navigation purposes.
While the Meacon scheme was being developed, it was
intended, as an emergency measure in case more jamming capacity
should be required, to earmark some one hundred T.77
transmitters, already installed at RAF stations for normal
communication purposes. In this way the whole of the country
could have been covered in clusters or groups of RAF jammers,
each of which would have been capable of dealing with German
beacons. The need, however, for this measure did not arise and the
scheme was never implemented.34 The first Meacons were ready
during July, at the start of the Battle of Britain.35 Air tests were
conducted immediately to prove the efficacy of the first station
based at Flimwell, near Tunbridge Wells.36 (See Figure 7) Full
results of the tests, however, were not available until two months
later when they indicated that crews of Luftwaffe aircraft, whilst
over the United Kingdom, could experience errors of between 9
degrees and 59 degrees when using beacons based in France.
Early in the following month, Dowding wrote a letter to the
Under Secretary of State for Air asking for immediate action to be
taken against these beacons.37 Fortunately, this requirement had
33 Post Office Eng. Dept. Radio Reports Nos. 597, 598 and 599, Post Office Instruction GB1, the GB Scheme, quoted in PRO Air 41/46, p.7.
34 PRO Air 26/580, p.2; PRO Air 20/8953 E.4A.
35 PRO Air 41/46 pp.7-8; PRO Air 41/46 App.“C”, Fig.1; PRO Air 26/580.
36 Laurie Brettingham, Beam Benders, Royal Air Force No 80 (Signals) Wing 1940-1945, p.18.
37 PRO Air 26/580; PRO Air 20/8963, E.4A.


75
AIR 41/46
Figure 7
Meacons & German M/F Beacons


76
been foreseen by the BBC and the GPO, and more powerful
Meacons designed. Some fifteen equipments were thus operating
by the end of the month. These were positioned at Flimwell,
Harpenden, Templecombe, Henfield and Petersfield. Air tests
continued during the Meacon build-up period and at the same time
comparative field strengths were obtained of German beacons and
RAF Meacon equipment.38 Such was the concern, however, felt
about the threat posed to the United Kingdom by the employment
of these aids that, at one time, use of the BBC's high-powered
transmitters was contemplated for jamming the whole band of
frequencies employed by the German Medium Frequency system.
Ten transmitters would have been required, the frequency of each
transmitter being modified to vary over a band of between 30 to 40
Kcs. But unless these had been operated in synchronised groups of
at least three, the Luftwaffe could have used them as beacons for
its own crews, thus outweighing any advantage of employing them
as jammers.39
The RAF airmen operating the Meacon equipment needed
much skill. Not only were they required to be fully conversant with
the Meacon itself, but had to be aware of the German call-signs
and the frequencies allocated to German beacons, together with
their radiated power and location. Moreover, the success of the
system was jeopardised every time the Germans switched
frequencies and/or beacons.40 Fortunately the RAF Y 'Listening'
Service, especially No. 61 Wireless Unit, under the command of
Wing Commander W.G. Swanborough, based at RAF Cheadle,
38 Ibid.
39 PRO Air 40/2242.
40 PRO Air 41/46, p.8; Ted Sweet, Enemy below!, pp.27-28.


77
knew both the frequency and the make-up of the Luftwaffe call
signs.41 Other factors also had to be taken into consideration. The
allocation of meacons to German beacons by the RAF Controllers
depended on the following: the number of Luftwaffe beacons in use
at any one time, the intended target or aircraft tracks, the power of
available meacons, the extent meacon transmissions would affect
bearings of beacons of different power, and the fact that meacons
could not be employed if sited on a line joining a German beacon
and the aircraft concerned, together with a number of technical
matters such as frequency spacing, harmonic values and receiver
capabilities.
5. Formation of No 80 (Signals) Wing
On 25 July, 1940, early in the first phase of the Battle of
Britain, while Luftwaffe aircraft were attacking convoys in the
channel, the Assistant Chief Of Air Staff (Radio) called a meeting at
the Air Ministry, to discuss how radio countermeasures against
Knickebein and the German beacons could best be organised. It
was decided that the useful application of such measures could
only be achieved by an officer having a complete knowledge of
German aircraft movements over or near the United Kingdom.
Early control was thus placed in the hands of HQ Fighter
Command. It soon became apparent, however, that RAF radio
countermeasures would be required on an ever-increasing scale,
involving a much greater organisation than hitherto envisaged.
Consequently, at a similar meeting held four days later, a decision
was taken for the establishment of a special formation, to be
known as No. 80 (Signals) Wing, which would assume
41 Aileen Clayton, The Enemy is Listening, p.60; PRO Air 20/163 and App.11; F.H. Hinsley, British Intelligence in Second World War, vol.1, p.323.