Dilly

by Batey, Mavis;

  Wilfred Bodsworth was now in charge of the Italian and Spanish traffic, leaving Dilly free to concentrate on the German naval indicating system as a means of breaking the machine. Alastair Denniston wrote that ‘Knox had made considerable progress in his diagnosis until April 1937’, but the navy then introduced a new procedural complication of bigram tables for the indicators and Dilly concentrated on unchanged army and air force traffic. John Tiltman remained in charge of the GC&CS Army section and a new air section to advise the Air Ministry, headed by Josh Cooper, had been set up in 1936. The discriminants (the groups in the message preambles denoting the particular network cipher system) of the new army/air force traffic between Germany and Spain were isolated by Tiltman’s deputy, Frederick Jacob, and its message indicators identified by Tiltman.

  Hitler’s first belligerent move had been undertaken in March 1936 when over 32,000 soldiers and armed police entered the Rhineland, which had been demilitarised under the Versailles treaty. Although it transpired that Hitler would have withdrawn if France had taken action, nothing was done by Britain and France in response to his violation of the treaty, but eavesdropping was stepped up. This was the period when Tiltman made a breakthrough identifying what he described as ‘throw-on’ message indicators used by the German operators when, for reasons of clarity, they were told to tap out the setting of the three wheels on the fixed message setting twice and put it at the beginning of their message. Tiltman swiftly realised this meant that this would be likely to produce repeat letters in the key-block, the set of indicators at the start of the message, at positions 1 and 4, 2 and 5, or 3 and 6. If, for instance, there was an M in the first position, invariably there would be a certain letter, say G, in the fourth position, and so on; this proved that the indicators were on the same setting and ripe for exploitation.

  In the autumn of 1938, Admiral Sinclair, anxious to increase co-operation with France, authorised Denniston to invite Bertrand over for a council of war. Bertrand, the man whom Denniston later called ‘a pedlar and purchaser of foreign government cribs’, arrived on 2 November 1938 and handed over a large number of documents, including original German material relating to Enigma that had been obtained by Asché. The French material was so important that Denniston wrote to Sinclair the same day asking permission to hand over a significant amount of different material in return. ‘We have received about 100 photographs of codes of which one might well have had great value in the event of war with Germany last month,’ Denniston told Sinclair. The French also handed over a full description of the Germans’ own communications intercept operations, some reconstructed German and Italian codebooks and a considerable amount of intercepted German and Italian telegrams. But the most prized documents were without doubt ‘photographs of documents relating to the use of the Enigma machine, which did increase our knowledge of the machine and have greatly aided our researches’, Denniston told Sinclair. ‘Our main reason for seeking this liaison in the first place was the desire to leave no stone unturned which might lead to a solution of the Enigma machine as used by the various German services. This is of vital importance for us and the French have furnished us with documents which have assisted us but we are still doubtful if success can be obtained without further documents.’ Sinclair immediately authorised the exchange.

  The conference with Bertrand took place the following day and was held for security reasons at Sanctuary Buildings, Great Smith Street, a few hundred yards away from the Broadway headquarters. It was attended on the British side by Denniston himself, Oliver Strachey, as chief cryptographer, Tiltman and Dilly. The morning session began with a discussion of the various German armed forces Enigma material the French had produced, followed by a presentation by Tiltman on the British work on the indicators for the Enigma keys. After lunch at Simpsons in the Strand, Dilly explained the methods of breaking the latest commercial Enigma machines. The French were impressed. ‘It appears to us that their cryptographic work is less ambitious than ours,’ Denniston said. ‘They have worked on the German and Italian unreciphered codes with success and on the German military [double transposition] hand cipher.’

  Bertrand was subsequently given the opportunity to see the flourishing Italian and Spanish section and Dilly’s methods of codebreaking and was promised a regular supply of decodes. ‘I think he was impressed by our success and by the ability of certain officers and it might well be that this had an important bearing on his subsequent action,’ Denniston later recalled. The whole Spanish situation was immediately apparent to the wily Bertrand, who understood that if Franco won his war against the Republican government and still used the same Enigma machine, France could keep an eye on its neighbour’s relationship with Germany, through its intercepts; bearing that in mind, Bertrand ‘salvaged five Spanish Republicans who had worked at Barcelona’ and installed them in Paris as intelligence officers in his new Spanish party.

  There was an urgent request from the British for more material from the French agent and before the end of the year Bertrand handed over the German users’ manual for Enigma, which had been given to Rejewski in 1932. Schlüsselanleitung für die Chiffriermaschine Enigma, the directions for setting up the machine which, unbelievably, included a genuine example of a ninety-letter stream of text in both clear text and cipher, complete with key setting. This authentic example was soon replaced by a fictitious one in subsequent manuals, when someone in the German cipher authorities became aware of the blunder. The French material was passed over via ‘Biffy’ Dunderdale and arrived in GC&CS in the red-lined file covers in which SIS distributed its intelligence material, which we called ‘Scarlet Pimpernels’. If only someone had recognised the value of Bertrand’s version with its crib for GC&CS in 1932, Dilly might well have broken Enigma by 1938.

  When Dilly finally received it six years later he immediately tried out his successful method for recovering wheel wiring, as he had done for the Italian and Spanish machines, but this time taking the German Stecker complication into account. Dilly had already decided that the Stecker merely added a substitution on the text letters entering the machine and the inverse substitution on the enciphered letters emerging. However, the way forward was not as easy as he thought. When Dilly was continually frustrated by not being able to recover the wirings by his well-tried crib methods, he feared that the diagonal, the entry connection from the keyboard to the wheels, was not QWERTZU, the typewriter order common to all the un-Steckered commercial machines he had worked on. QWERTZU was tried backwards to no avail and then came the awful thought that the Germans had achieved the ultimate Enigma machine complication – that of a random entry plate connection.

  Bertrand set up a meeting with the Poles and the British in Paris in January 1939, which Denniston said was held in ‘an atmosphere of secrecy and mystery’. The Poles were very suspicious since the Munich appeasement with Hitler in September 1938 and still not prepared to reveal their Enigma successes. Denniston and the three codebreakers Dilly, Foss and Tiltman attended on the British side but the Polish representatives did not include any of their real codebreakers, with whom Dilly could have had a meaningful discussion. Hugh Foss recalled how annoyed Dilly was that ‘at these two interviews, the Poles were mainly silent but one of them gave a lengthy description in German of the recovery of “throw-on” indicators’. This was Major Maksymilian Ciężki of the Polish Cipher Bureau, who was in charge of the German section and had carried out the initial Polish work on the Enigma machine, before handing the material over to newly recruited mathematician codebreakers in 1932.

  During Ciężki’s exposition at Paris, Dilly kept muttering to Denniston ‘but this is what Tiltman did’, while Denniston ‘hushed him’ and told him to listen politely. Thinking that Ciężki must know how the machine worked, Dilly naturally asked him the burning question as to what the diagonal he had assumed to be QWERTZU was. Dilly soon realised that the Polish officer knew nothing about the actual breaking of the Enigma machine and it was all a waste of time. He frustratedly
wrote in his assessment of the Polish work on Enigma: ‘Practical knowledge of Qwertzu Enigma nil. Had succeeded in identifying indicators on precisely the methods always used here, but not till recently with success. He [Ciężki] was enormously pleased with his success and declaimed a pamphlet, which contained nothing new to us.’ It is clear that Dilly brought no information that would help him back from the Paris meeting with the Poles.

  Dilly was also unimpressed by the French description of their attempts to solve Enigma, which they ended with a flourish and a dramatic ‘Voici la méthode française’. But he did strike up a lasting friendship with Bertrand’s chief cryptographer, Henri Braquenié, at the meeting and according to Foss, who was present at the time, the French were delighted when Dilly demonstrated how to use his rods and by the next meeting had made a set of reglettes of their own.

  Denniston rightly realised that the Poles had agreed to the Paris meeting because they had run into difficulties in April 1938 when the Germans changed the indicating system. Colonel Gwido Langer, head of the Polish Cipher Bureau, had been told by Bertrand of Dilly’s progress in attempting to break Enigma and was anxious to seek his help. The minutes of the Paris meeting recorded frustration on both sides, Bertrand said, and ‘it seemed that the work had arrived at an impasse out of which only information from an agent could provide a way. A technical questionnaire was drawn up, as simple as possible, to give to the agent.’ Dilly asked Bertrand whether the agent could obtain sixteen alphabets enciphered on the Enigma machine for him, if he could not recover the wirings themselves, but any spy would be lucky to get away with half an hour’s noisy clonking of the wheels and the idea was abandoned. However, Dilly never lost hope that his methodology would finally succeed in spite of the pessimistic belief elsewhere in GC&CS that Scherbius’s claim that Enigma could be unbreakable if used properly was proving correct. ‘Nothing is impossible’ was after all Dilly’s motto.

  Up to this time, Dilly’s only assistant on the German Enigma machine had been Tony Kendrick, but after the Paris meeting GC&CS decided to apply for a mathematician and appointed Peter Twinn from Brasenose College, Oxford. He recalled his first day at Broadway Buildings, where he found

  the people working on the Enigma were the celebrated Dilly Knox and a chap called Tony Kendrick, quite a character, who was once head boy at Eton. There was a slightly bizarre interview with Dilly who was himself a bit of a character to put it mildly. He didn’t believe in wasting too much time in training his assistant, he gave me a five-minute talk and left me to get on with it.

  Denniston now went further and made the rounds of the universities to bring in former colleagues and new talent, as Josh Cooper recalled:

  He dined at several high tables in Oxford and Cambridge and came home with promises from a number of dons to attend a territorial training course. It would be hard to exaggerate the importance of this course for the future development of GC&CS. Not only had Denniston brought in scholars of the humanities, of the type of many of his own permanent staff, but he had also invited mathematicians of a somewhat different type who were especially attracted by the Enigma problem.

  Alan Turing, of King’s College, Cambridge, went to one of the first of the training courses on codes and ciphers at Broadway Buildings; this was of a general nature and it is unlikely that Dilly was present, given his views on being thrown off at the deep end as far as breaking Enigma was concerned. However, Turing was put on Denniston’s ‘emergency list’ for call up in event of war and was invited to look in on Dilly’s small group to hear about progress with Enigma, which immediately interested him. Unusually, considering Denniston’s paranoia about secrecy, it is said that Turing was even allowed to take the ‘crib message’ back to King’s, and that ‘he sported his oak’, the then popular euphemism for working behind a closed door to discourage visitors, as well he might. They had begun to lose faith in Bertrand’s miraculous operators’ manual cipher and text crib and to think that what they were given to believe was an authentic example of cipher and plain text was after all fictitious. However, a meeting was arranged in Warsaw in July 1939, when the desperate Poles finally revealed, at the eleventh hour, how straightforward Dilly’s QWERTZU problem was and how near he had been to winning the Enigma race.

  SIX

  The Warsaw conference

  ‘Nous avons le QWERTZU – nous marchons ensemble’

  Rumours of war had turned into the certainty of war by the time the tripartite conference of French, British and Polish codebreakers was called in Warsaw in July 1939. Hitler had demanded the return of Danzig and when the Poles refused tension reached breaking point, especially given that the Poles could read from the Enigma messages that tanks were about to assemble on their borders. Finally, when the Nazis marched on Prague in March, Britain gave an undertaking that the government would declare war on Germany if Poland were invaded. The situation was desperate when the Polish Cipher Bureau invited GC&CS to their war station at Pyry in the Kabackie woods near Warsaw. A decision had been taken at the highest level that, with the imminent threat of war, the time had come for their Enigma secrets to be handed over. A special request was made that Dilly Knox should be present. This was difficult. Dilly had been ill and the doctors had recently diagnosed lymphatic cancer. He had just had his first operation and was at the time suffering from influenza, but he insisted on accompanying Alastair Denniston. His family remember him staggering out of bed, ashen grey, but determined.

  A fortnight before the departure, Rear-Admiral John Godfrey, the new director of naval intelligence, who was anxious to have personal contacts with GC&CS, had visited Courns Wood to renew an acquaintance made in the First World War. As a young officer on the staff of the Commander-in-Chief Mediterranean he had visited Room 40, where his brother Charles, headmaster of Osborne Royal Naval College, worked in the school holidays. Godfrey’s mission at that time was to help organise intelligence for the Mediterranean fleet and he lectured to Greenwich Staff College on the contribution made by intelligence to naval operations. He would have met ‘Blinker’ Hall, Denniston, Birch and Dilly in Room 40. His objective in 1939 was to make sure that naval intelligence would make the utmost use of signals intelligence and he kept himself informed about the progress of the attempt to break Enigma. Learning about the forthcoming Polish conference he wanted to ensure he had an official representative. This was to be Commander Humphrey Sandwith, who was in charge of the Admiralty’s network of intercept and direction-finding stations. The Knox boys were amazed to see an admiral in full dress uniform in their dining room, but it would not be for the last time.

  Dilly and Denniston travelled by train on 24 July as they wanted to see Germany for the last time before all hell broke loose. They arrived in Warsaw the next day and were met by Colonel Gwido Langer, the head of the Polish Cipher Bureau, who took them to the Hotel Bristol, where they were to stay. Bertrand was the perfect host and took them out to dinner at the celebrated Restaurant Crystal, where they were joined by Commander Sandwith. Bertrand told Penelope Fitzgerald in 1974, when she was writing The Knox Brothers, that ‘the naval commander ate and drank too much, Denniston remained discreet, and Dilly appeared froid, nerveux, ascète, scarcely touching any of the courses and concentrating only on the matter-in-hand.’ In 1948, Denniston wrote a full report he called ‘How News was brought from Warsaw at the end of July 1939’. Other first-hand accounts were also written by Bertrand and the Poles, but only thirty years later, and there is a discrepancy about the actual date of the two-day meeting. Denniston, however, had his pocket diary in front of him when he wrote and has the correct date. He records that ‘the 26th (Wednesday) was THE day. The Poles called for us at 7am and we were driven out to a clearing in a forest about 20 kilometres from Warsaw.’

  The 26th was not THE day for Dilly, however; it was in fact a disaster as all he wanted to do was to meet the cryptographers and sort out his QWERTZU problem, but if they were there they played no part as it turned out to be what Denniston called ‘a
prolonged full-dress conference’ with Colonel Langer. All his life, Dilly had objected to what he called administrative ‘window-dressing’ and the ‘prolonged full-dress conference’ with senior officers who had no idea how to break Enigma doing all the talking was always going to bring out the worst in him. To make matters worse it was Maksymilian Ciężki, chiefly concerned with the wireless organisation, who was delegated to lecture on how the Cipher Bureau had broken the Enigma machine. Albeit a very pleasant man, it was Ciężki who had annoyed Dilly at the Paris meeting as his knowledge of the issues was limited and he did not understand Dilly’s problem. However, be that as it may, there was no doubt that the Poles had somehow broken the German Enigma machine and it certainly made Denniston’s day when they were shown an actual model they had made of it and the mechanical devices used to break messages.

  But it did not make Dilly’s day. Denniston subsequently described how he sat in ‘stony silence’ as Ciężki gave his lecture:

  Knox, as our expert, was alongside Ciężki and in the best position to follow his explanation. He, however, reacted very badly to the explanation, which took about three hours with a break for a cup of tea. I confess I was unable to understand completely the lines of reasoning but when, as second part of the conference, we were taken down to an underground room full of electric equipment and introduced to the ‘bombs’ I did then grasp the results of their reasoning and their method of solving the daily key. Knox accompanied us throughout but maintained a stony silence and was obviously extremely angry about something. It was only when we got back into a car to drive away that he suddenly let himself go and, assuming that no one understood any English, raged and raved that they were lying to us now as in Paris. The whole thing was a fraud he kept on repeating ‒ they never worked it out ‒ they pinched it years ago and had followed developments as anyone else could but they must have bought it or pinched it.