R.V.Jones on II)_•..· ~ll[;ii / &1~11 New Scieotlst 23 February 1978 493 Pulling the crooked leg Published next week are the memoirs of the wartime head of Air Ministry Scientific Intelligence. Here he reveals some of the operations of the "most secret" war successfully waged in the backrooms of Whitehall and In scientific laboratories all over Britain against the Germans* PrMessor R. V. Jones FRS is pr-olessor of natural philosophy al the Universit..v of Aberdeen. At the outbreak of war he was researching infrared spectroscopy at the Cla:rend.011. Laboratory, Oxfprd I was always aware that,. exciting though Intelligence wast and im• portant though its results mani festly were, it was on a lower plane of difficulty than research in pure science.. Intelligence is a parasitic activity; in that you are always trying to discover what some other man has already done. in contrast to entering an un charted field yourseH. One of the greatest difficulties in scientific research is to build up your observational -experience in this new field, and to develop concepts that have never entered any huanan mind before. They may even appear to contradict long established principles, as when Einstein proposed the equivalence of mass and energy, ,or when de Broglie postulated that material particles could also behave as. waves" or when Bohr bad to conclude that the radial acceleration of electrons in his orbits did not make them radiate. Sometimes in lntellig,en-ce we experienced this kind of difficulty, when for example it was necessary for us to postulate that radio waves bent further round the Earth than our own expert$ thought, or that rockets could be made with a range greater than 100 miles; but all the time I knew that we were trying to discover something that bad already been discovered and formulated in the minds of our Cerman opponents, and that it therefore should be within our mental gr.asp. To that ext~nt I felt that we were parasitic, and tackling a basically easier job than that of research in pure science. Even so, we sometimes had difficulties comparable with those of scientific innovators when we bad to persuade our experts to abandon some of their bithert.o accepted con cepts. Moreover, the methods we used in gathering and collating information wen? much the same in principle as those employed in pure science. Where we oould claim to be genuinely •creative was in de\'eloping new methods of Intelligencet such as listening to radar transmissions, and in welding them into a great system for observing the enemy by as many means as possible"' and directing this •MNc Seavt W«:.~ l. V. Ion• (WMl.11111 Ma"'8loft. '6•'5). ""' which th.-. uar,a. ha,,• ._. ak-. Is ,-,11111ithN on 'D felNwrr. system and correlating the infor~ation that it obtained by these means into a comprehensive reliable estimate of enemy intentions. We were remarkably fortunate in our opportunity. Just as the impact of radio in the 1920s gave a unique chance for every man to dabble in the "marvels of science" by making his own receiver-a task complex enough to be fasdnating without being so mm.plex, as television later wa.s, that it was beyond the competence of the average man-so it was with Scientific Intelligence in the Second World WarI and for much the same reason. The very development in science and technology that led to every day radio in the 1920s also led to the radar and radio navigational systems of the Second World War, and these were relatively simple to understand and. if necessary, frustrate. Moreover, these developments in radio were of such universal application in military technolog-y that they gave me the entry to fields which at first sight might have seemed quite remote. Radar provided the key to the German night defences, and thus enabled me to attack those defences more fruitfully than through any other channeli an.d it also enabled me to attack the ftying bomb in a positive manner by going for the German radar plots in their Vl trials at Peenemiinde. J was therefore able to redu.ce some of our major Intelligence problems to, the field that by good fortune I knew best. Possibly the opportunity of Enigma might be vi w d in the same light, for it involved radio communication at a stage of sophistication that was just within the limits of human ingenuity to "break". At the outbreak of war, September 1939, I was billeted at Bletchley with Sir Kenneth and Lady Macdonald at Winslow, along with Commander Edward Travist who hap pened to be Deputy Head .of the Government Code and Cip-her School, the cryptographic headquarters that was officially part of MIG. The head of the school was Com mander Alexander Denniston, whom Travis: was to suc ceed in 1942,. but who bad laid the foundations. of our brilliant ayptographic successes. In our long evenings together Travis discussed with me his problems in CQ-pto grapby, and in particular the problem of trying to "break" the German Enigma machine. New Sdentist 23 February 1978 TIii• EnJgma encoder The Enigma machine was a very ingenious arrangemcn_t of cogged wheels,. each one of which had a sequence of studs on both sides. with each stud on .one side being connected by a wire to a pin on the -0ther side--the exact arrangement of the. connections being one of the secrets of the machine and the pin making contact \vith one of the stud on lhe next ,vheel The machine had a typewriter keyboardt and it was worked rather like a cydometer: every time the n1achine was opera~ to encode a letter. one wheel would be turned by one space; after tbi ,vbeel bad moved by enough spaces to turn it through -0ne revolution, it \YOuld click its neigh bouring wheel by one spaoo. The. wheels were thus never in the same position twice. The basic encoding was effected by the passage of an electTic current through lhl? stu_ds so that when a letter was to, be encoded. the appropriate key would be pressed ou the keyboard, and the resultant _cod~d letter would be determined by the appropriate conducting path through the studs, the studs on one wheel maklnJ.? suitable contact with the pins on the neighbouring wheel A further touch of ingenuity was to add a reversing arrangement at the edge of the third wbeel, a,ain with st11ds cross-connected so as to send the current backwaTds th:Fough the wb.eets by yet another path. Tbe returning current lit a smaH electric bulb which illuminated a particular letter on a second keyboard. and thus indieated the enciphered equivalent of the letter whose ~Y had originally been pressed. t ..l!I8e 1i--:_Ju1c;!z, lI1•i' Figure J A j four"'Totor > Enigma which I the German ,;11 Nav1J med. It l defied the best I' etrartl of c Bletchlet, PMk ~ untit JHS .t.!. L - - - -- -- -- - - - - -- - - - - -- - -- - - - - - - - - - - - - - -- - - - - -- --- L Sometimes, as with Knickebein, the German aircraft navigational system, a single short decode provided the clinching evidence. And because there was every Jikeli· hood that the Germans felt that they were secure in Enigma, even a single message was likely to provide an anchor of truth on whlch any explanation of German activity could be confidently based, or a teuchstone against which previously formed theories of German intentions could be tested. Care was of oourse necessary-although any one decode was Jikely to be 100 pet cent reliable, it might well contain much less than the wboJe truth-a fact that must always be borne i.n mind regarding information from any source, however reliable. But the confidence with which Enigma decodes could be used in constructing or testing theories of enemy intentions was outstanding among aJJ the sources available to us. Battle of the beams On the morning of 12 June, 1940, I visited Group Captain Blandy, the head of the RAF "Y" Service, which inter cepted German radio signals. He banded me a scrap of paper saying, "Does this mean anything to you? It doesn't seem to mean much to anybody here." I read: "XNICllEBEIN. KLEVE, IST AUF PUNKT 53 GRAD 24 MINUTEN MORD UND ElN GRAD WEST ElNG:EBICHIE1 ." The word "Knickebeinn (crooked leg ) I had ear1i r noticed in a fragmentary entry on a paper salvaged in March from a shot.down Heinke} aircraft. Information from a German prisoner suggested it to be some sort of beamed beacon. 0 Klev " could be the west German town that we koe,v as Cleves. where Anne came from . If so the translation would run : ''Cleves Knicltcbe_in is confirmed (or established} at position 53° 24 minutes north and 1• west." The geographical position referred to was a point in England, roughly on the Great North Road a mile or so south of Relford. I immediately told BJandy that it meant everything to me, and that it suggested lbat the Germans liad a radio beam transmitter called Knickebein set up at Cleves, on the nearest German soil to England. and that the existence of the beam bad been confirmed one way or another at this position over England. I quickly recognised that it was a decoded message, because I knew that during the preceding hYo months Bletchley had begun to be suc cessful in decoding some of the Enigma messages. This particular one had been sent by the Chief Signals OOicer of Flieger Korps JV at 1455 hours on 5 June, and had been decoded four days later. I had to go to the Cabinet Office to see Professor Frederick Lindemann, in response to a question about German radar, and told him that I bad just received the· Kniclcebein message, and that I was convinced that the Germans had an intersecting beam system for bombing England; and if they could make narrow beams for navi gation they could also make narrmv beams fm- radar. Lindemann immediately said that the beams would not work for radionavigation, because they would have to use short waves which would not bend round the curvature of the Barth. Armed with some computations by T. L. Eckers ley, I told him that, contrary to what he supposed, they would. The bombers available to Flieger Korps IV were Beinkel ms of Kampf Geschwadern 4 and 27. Whatever equipment was used for receiving the Knickebein beam must be capable of being fitted to this type of aircraft. Squadron Leader Denys Felkin, chief interrogator at Bletchley, had prisoners from the bombers shot down dur· ing the preceding few nights, so I briefed him about the information that I needed. He duly interrogated the prisoners without at first get ting anything of value. But when the prisoners were alone one of them said to another that no matter bo\v hard we looked ,ve would never find the eq_uipment This could not have been a better challenge because it implied that the equipment was in faet under our nose$, but that we would not recognise it. I therefore obtained a copy of the full t chnicaJ examination of the Heinkel m that had been shot do\vn in the Firth of Forth raid, and looked especially at the various items of radio equipment. The only item that could possibly fill the bill was the receiver that was carried in the aircraft for the purpose of blind landing. It ¥.~as labelled as E.Bl.I (which stood for Empfanger Blind I -blind landing receiver type l ) and was ostensibly for the normal purpose of blind landing on the Lorenz beam system, which was by then standard at many aerodromes. N. Cox Walker at Farnborough, who had evaluated the equipment, then told me that although there was .nothing New Scientist 23 February 1978 495 · - ,\((Ullt ,R((fPf10,t &8C. £N11(,e,t PO·II~ C.E. ,tl\~D- thl<'TE- . • .. ,,,to,1"'""'~1:,,._-,c:,.. 1 - t-1-._ AtTtn,, tr. O~N(. A~~ i>O' FigUTe 2 (above) The L~rger', musczge and s1'etch. fop right R. V. Janus sketch of the HagtLB .Kn.ickabein. Bottom right Beinhel JU wUh cmten.noe for X-oeam guidance unusual about the blind landing receiver, it was much more sensitive than would ever be needed for blind land ing. So that was it. I now knew the receiver, and the frequencies to which it could be tuned, and therefore on which the Knickebein beam must operate. And in a short time we heard the beams for ourselves. Although it was worth squeezing every drop 8f information out of the Enigma decodes, it would have been dan• gerous to rely on them too much, and thus to neglect other sot1roes. Io a sense, cryptography was the most vulnerable sour,ce of all in that it collld have been extinguished at any time by a few simple changes in the Enigma machine. At the end of every investigation I therefore looked back to see how far we could have gone without Enigma As the outstanding example, it was reassuring to· find that we would very probably bave raided the rocket-launching sites at Peeoemiinde without any help from Enigma. This observation is not intended in the slightest to belittle the enorm.ous contribution made by those who brok~ the Enigma traffic-quite the reverse. And it is a pleasure to know that in a war in which scieor.e, and especially pbJsical science, gained great esteem, the cootn'butions of our colleagues in mathematics .and in some of the arts subjects can at last be publidy recognised. Det ■ ctin1 the •v• llodtet ...II The message about a rocket that we received from a Danish chemical engineer in December 1942 resensitised us to a possibility which, although I had reported it in 1939, had no more than stayed in the background of our thoughts over the intervening hectic years with the beams and German radar. A report received fr-om Oslo had men• tioned Peenemiillde. where, it had said, radi<>