The Bletchley Park Codebreakers

by Michael Smith

  This was an exceptional disappointment: for the next six months we demonstrated the efficiency of Banburismus, cribs and bombes by breaking almost every day, sometimes very quickly, occasionally with a few days’ delay. We had the satisfaction of learning that the resulting intelligence, used with great discretion in order not to compromise the source, led to a dramatic reduction of sinkings of merchant ships by U-boats in the Atlantic.

  It was during this period that I was lucky to find a successful crib for an Offizier message. Such messages, thought to require a higher degree of secrecy, were encrypted by an officer using different pluggings (Stecker) and one of twenty-six starting positions of the wheels. At that time, the pluggings changed every day and the twenty-six positions every month. The encrypted result was then encrypted a second time by the regular operator with the normal key for the day, with a preamble featuring the word Offizier and a name (Anton for A, Berta for B, etc.) indicating the starting position.

  I was not expecting to be successful and went home on leave before the testing on a bombe was complete. Wylie promised to confirm a positive result by sending me a telegram containing the name of a fish. When a telegram arrived with the word ‘pompano’ I had to look it up in a dictionary to make sure that ‘pompano’ was a fish. The breakthrough resulted in more knowledge about the content of Offizier messages which subsequently helped us to read most of these signals without great difficulty.

  We dealt successfully with a change in October 1941, when the Germans split the traffic into two keys, one for U-boats in the Atlantic and one for the rest. We called the U-boat key Shark and the other Dolphin. For some reason the U-boats in the Arctic, north of Norway, remained on Dolphin.

  We were forewarned by some messages that a more serious change would occur on 1 February 1942. On that day, the Enigma machines used for Shark started to use a fourth wheel. The change multiplied by twenty-six the number of combinations of variables to be tested by the bombes – it also made Banburismus impossible. Except on rare occasions we did not, at that time, have enough bombe capacity to try possible cribs. We therefore broke only three Shark keys between February and mid-December 1942. The consequence was an upsurge in the number of sinkings, which reached dangerous levels for the rest of that year.

  I have been asked whether our prolonged inability to break Shark gave us a sense of guilt. While we knew the seriousness of the situation I cannot say that we felt guilty. First, we genuinely felt that, without more captured material, there was no short-term solution. Secondly we knew that there was a long-term solution because of plans, in collaboration with the Americans, to build more powerful bombes capable of coping with the four-wheel machines. Thirdly we were still regularly breaking Dolphin (the other main key) as well as, from the summer of 1942, a separate key called Porpoise used for traffic in the Mediterranean. We did have a sad time in July when we were late in breaking a crucial day while the Arctic convoy PQ17 was being slaughtered by U-boats and aircraft.

  In his chapter on ‘Breaking Naval Enigma’, Ralph Erskine has given an account of the steps which enabled Hut 8 to resume its breaking of Shark from mid-December 1942 to June 1943 with the aid of ‘short signals’ used by U-boats for weather reports (WWs) and operational reports (B-bars). This success could not have been achieved without the men from HMS Petard, who gave their lives in capturing the necessary codebooks from U-559.

  The construction of successful cribs for WWs was then dependent on the breaking of a meteorological cipher in Hut 10 under Philip Archer; the result became known in Hut 8 as Archery. In the later stages essential information relating to B-bars was provided by Edgar Jackson, head of one of the Naval Intelligence sections in Hut 4 (afterwards Block B). Within Hut 8 a major contribution to this work was made by Michael Ashcroft whose promising post-war career at the Treasury was tragically cut short by his death from cancer in 1949.

  June 1943 marked the beginning of a new era for Hut 8. The first of the new bombes had arrived, capable of dealing with the variables of a four-wheel Enigma machine. Quite soon we had a growing arsenal of three-wheel and four-wheel bombes. This meant that we could do all the key breaking by cribs, without the help of Banburismus, even on Dolphin, which stuck to three wheels until 1944. In the following months there was a gradual exodus of talent from Hut 8: Wylie, Ashcroft and others left to join the Tunny section (Block F) under Max Newman, where they contributed to another of the great Bletchley successes. Finally, in autumn 1944, Alexander was transferred to work on Japanese naval codes and Patrick Mahon became head of Hut 8.

  In the last twelve months of the war all the breaking of naval keys was done by four cribsters: Patrick Mahon, Joan Clarke (later Murray), Richard Pendered and myself; we worked on a shift rota around the clock. All the main keys were broken regularly during this period. While some of the cribbing became routine we enjoyed our tasks after the bombes had identified a key’s wheel order and pluggings. We still had to work out the Ringstellung and the Grundstellung.

  With growing participation by OP-20-G, our opposite numbers in the US Navy, we coped successfully with the introduction of many new keys: they included Plaice for ships in the Baltic, Grampus for ships in the Black Sea, Narwhal for U-boats in the Arctic, Sunfish for blockade runners, etc. In one way this proliferation was helpful because the same announcement was often sent out in several keys. Having broken one of these we had a reliable crib for the others.

  Apart from these re-encodements, weather messages remained our most frequent source of cribs. On D-Day in 1944 we broke Dolphin at daybreak thanks to an undisciplined German operator who began his report day after day with WETTERVORHERSAGEBISKAYA. At other times the disciplines must have been reimposed so that reliable weather cribs disappeared for a time. We then had to turn to other sources, including the ‘gardening’ procedure described in Chapter 11. The areas where the RAF dropped mines were carefully chosen so that the German naval grid references contained no numbers for which there were alternative spellings (NUL or NULL for ‘0’, FUNF or FUENF for ‘5’).

  One day, while on duty in the morning, I was told by Intelligence that it was very important for us to read the next day’s messages as early as possible. Would gardening improve the chances of an early break.’ I thought about it and gave the answer ‘yes’. That night was stormy and I lay in bed worrying whether my judgement had been correct or whether I had needlessly endangered the lives of the air crews. I was extremely relieved when I heard next day that there had been no flying because of the bad weather.

  On rare occasions a successful crib was based on a guess that a message might contain an important topical announcement. The outstanding example occurred when the battleship Tirpitz was sunk by Bomber Command in north Norway in November 1944. We guessed that a certain signal might say ‘Tirpitz capsized’. It did and we were able to break one of the day’s keys.

  Although in the last phase the number of cryptanalysts in Hut 8 had dwindled to four, we were always dependent on a big supporting cast. First of all there were the wireless operators at the various interception stations who did a fantastic job. Picking up and accurately recording a short signal, lasting only a few seconds, must have required great skill and concentration. Then there were the ladies in Hut 8 itself, eventually about 130 of them, doing the clerical work and the typing; in the days of Banburismus they also had to punch the holes in the Banbury sheets. Finally, there was the work of running the bombes, which were located in several big houses around Bletchley. This was done by Wrens working under very spartan conditions. Looking back, I think that we did not give enough credit to all these people without whom we could not have functioned.

  The Germans responsible for Enigma security had tolerated all kinds of flaws but they became extremely active at the very end of the war. A complicated new system for determining the starting positions of signals was introduced on Dolphin in May 1945. We made plans to meet this challenge but it would undoubtedly have caused delays and it was perhaps fortunate that the war e
nded before the new procedures became effective.

  At the peak there were about 9,000 people working at Bletchley Park. With, I believe, only one exception, the confidentiality of the work was never breached either then or for about thirty years after the war. We had all signed the Official Secrets Act and never doubted that we could not talk about what we did during the war. Is it conceivable that such secrecy could be maintained amid the present culture of constant leaks?

  Robert Harris’s Enigma is a very good novel but it paints far too drab a picture of life at Bletchley. No doubt the meals served in the canteen featured dried egg, Spam, and other wartime delicacies: they may have been stodgy but they were perfectly palatable. Most of us were billeted on householders in a wide area around Bletchley and I do not remember many complaints. I have fond memories of the elderly couple with whom I lodged in Newport Pagnell; the wife was a wonderful lady who had been maid to a duchess. No duchess could have received better care than I did.

  Many of us had come straight from university and it was in many ways like having an extra four years of university life. We did work hard, taking unsocial hours for granted, but there was also a good social life. An active Dramatic Society put on plays and satirical revues of a high standard, there was a lot of music, and we played chess and bridge. Most men went about in old sports jackets and shabby corduroy trousers. Once when a visiting Admiral was taken around the site by the Director he is reported to have asked: ‘What are all these velvet arsed bastards doing here?’

  I had a happy time at Bletchley, not only because of the work but because Hut 8 was always a friendly place. There really was a spirit of camaraderie among the cryptanalysts and a sense of a common purpose. I can recall no personality clashes or big outbursts of temper. I attribute this to the fascination of the work, the satisfaction of getting results, exemplary leadership and, above all, the personalities of the individuals. I would like to conclude this account with recollections of some of them.

  From addressing each other by our surnames we soon switched to first names. There were two exceptions: one of these was Alan Turing, without whom Hut 8 might not have existed. It was he who, building on pre-war discoveries by the Poles, originated the methods by which the naval Enigma was broken. We all recognized his genius; perhaps for this reason he was known as ‘Prof’. We regarded him as eccentric but I cannot remember any specific eccentricities. By the time of my arrival in Hut 8 the basic principles of the work were well established so that there was less scope for his genius. He therefore spent more and more time on assignments outside Hut 8 and left altogether in late 1942. While he was with us he was always approachable and ready to help with technical problems. It may have been my fault that I did not find it easy to communicate with him.

  I could always communicate with Hugh Alexander, the former British Chess Champion, who had come in as acting head of Hut 8 because Turing’s great abilities did not include a talent for administration. He had a wonderfully quick mind combined with tremendous energy and enthusiasm. I still think of him as the model manager, always leading from the front. He treated us as colleagues but he could be very firm when it was necessary.

  Turing and Alexander have since died but Shaun Wylie remains active in his eighties. Alexander rightly described him as ‘easily the best all-rounder in the section, astonishingly quick and resourceful’. He was an outstanding leader who always set higher standards for himself than for anyone else. I have continued to admire his intellect and his integrity, more recently his superior skill in solving the weekly ‘Listener’ crossword in The Times to which we are both addicted.

  I have already mentioned the part played by Michael Ashcroft when breaking Shark was resumed in 1942–3 with the aid of short signals. He would now be described as a caring man; he had helped to rescue and educate at least one Jewish boy from Germany. At Oxford he was active in centre-left politics. We shared various interests and met frequently after the war. I felt a great loss when he died.

  Patrick Mahon was the obvious choice as head of Hut 8 when Alexander left in September 1944. He was exceptional among the cryptanalysts in being a linguist, not a mathematician. If this was a handicap, he amply compensated for it by great energy and a very methodical mind. It was he who discovered the shift system worked by some operators sending weather messages. He was given to strong views, with some youthful intolerance, but he was always popular because he had great personal charm. After the war he had a successful career in the John Lewis Partnership. We kept in touch but sadly his health failed and he died prematurely in 1972.

  Richard Pendered was the brightest of the younger cryptanalysts in Hut 8. He had a memorable success when he broke Shark for 27 May 1943, using a long crib, by a purely manual method, which he himself had refined. It was a superb technical achievement: the method was used again to find the wiring of a new fourth wheel and reflector which the Germans introduced on 1 July 1943.

  Joan Clarke, later Murray, was an excellent Banburist who later became an excellent cribster. It was a tribute to her ability that her equality with the men was never in question, even in those unenlightened days. She was kind and always good-tempered, but rather reserved. It was known that she had been close to Alan Turing but that nothing had come of the relationship. She never spoke about it, but when I met her again in 1993, at the launch of Codebreakers (the book of reminiscences of Bletchley, edited by Harry Hinsley and Alan Stripp), she said that she had not seen Hugh Whitemore’s play Breaking the Code because it would have been too painful.

  The other exception to the use of first names was Kendrick. I never knew what the initials F. A. stood for and it was something of a shock to find him listed in the index of Codebreakers as ‘Kendrick, Tony’. He was a member of Hut 8 from early 1940 until July 1942; it was said that any new suggestion had already been proposed by Kendrick at some earlier date. Severely crippled by polio, he was a very private man but he was courteous and kind, and he had a fine sense of humour. He was an even shabbier dresser than the rest of us; strips of tattered lining were seen to protrude from his threadbare suit. It was believed that this was his protest, as a career civil servant, against the abandonment of pinstriped trousers after GC&CS moved to Bletchley. Some time after the war I met him at a concert; he was working at the Ministry of Defence. ‘England is safe then,’ I said. ‘Yes,’ he replied. ‘I don’t interfere much.’

  When the war ended I could not tear myself away from decoding and spent a further year working on other ciphers. When I finally left to join the family business created by my father, I made sure that I could come back if a six months’ trial did not work out. The option was unnecessary: I am still involved in the business.

  Being at Bletchley during the war was a prime example of my good fortune in life. While most of my contemporaries were risking death or injury and enduring hardship I was living comfortably and doing exciting work. At the same time I could maintain my self-respect because the work was important. I know that I was very lucky.

  13

  BLETCHLEY PARK AND THE BIRTH OF THE VERY SPECIAL RELATIONSHIP

  STEPHEN BUDIANSK

  Introduction

  Chapter 13 describes the wartime events that gave birth to the unprecedented - and, more than a half century later, still enduring - ‘special relationship’ between the British and American signals intelligence services. Through a combination of wartime necessity, some shrewd political calculation, and not a few deft acts of individual diplomacy, Britain and the United States agreed to throw open the doors to one another on many of their most closely guarded secrets. It was far from a foregone conclusion that they would. Even after the two allies subscribed to formal arrangements on Sigint co-operation during the course of the war - the Holden Agreement (on naval Sigint) and BRUSA (on attacking the army, air force and secret service codes and ciphers of the Axis powers) - there were many forces at work to prevent co-operation from becoming anything more than symbolic. The British on several occasions sought to keep control of
the dissemination of Sigint from Enigma firmly in their hands; the Americans, for their part, completely refused to share with their ally the US Navy’s extremely secure Electric Cipher Machine Mk. II (the Army’s Sigaba), even when that refusal severely hampered the Allied war effort. Yet through all of the mutual suspicions, tensions and jockeying for position that inevitably occurred, a genuinely co-operative relationship was forged, that paid off dramatically during the war (and afterwards). This was particularly true of the mobilization of American industrial might to produce the much-needed four-rotor bombes that took over the solution of the Atlantic U-boat Enigma problem during the last two years of the war.

  Surprisingly, the US Army and Navy were at times prepared to trust their ally more than they trusted each other. Dr George McVittie, the head of GC&CS’s meteorological subsection, was astonished to find, during a visit to the United States in September 1942, that Commander Joseph Wenger in OP-20-G was willing to reveal secrets to him which he would not pass on to two Army codebreakers. GC&CS had to be very careful not to disclose the contents of the Navy’s Sigint pact to the Army and vice versa: the Navy did not send a copy of the Holden Agreement to the Army until mid-1944, two years after it was signed.