‘The new German security measures of all kinds might, properly handled, have virtually stopped the flow of operational intelligence from Hut 6 to Hut 3,’ said J. M. ‘Max’ Aitken, the official historian of Hut 6.
Very largely through German mistakes, this result was never achieved. This is not to say that our success was unaffected but on the whole the luck of Hut 6 held good and to the end we decoded currently most of the vital operational traffic. On the Army side, in particular, 1944 witnessed an immense advance. Though we should not forget the valuable intelligence provided by the African Army keys in 1942–43, still Hut 3 had never previously seen Army traffic of such high quality as on the best keys of 1944 – the Bantams, Ducks and Puffins. The importance of Army keys relative to Air constantly increased and towards the end when the Air difficulties were most acute the Army decodes sometimes surpassed the Air in number as well as quality. This was of course a reversal of the situation that prevailed for most of the war, but the Army experts who had in general the hardest cryptographic tasks cannot be grudged this final hour of triumph. In 1944–45, first Italy, then the West, finally even the East was held in fee and, on the Army as on the Air, the cryptographic encirclement of Germany was complete.
Asa Briggs, later the distinguished official historian of the BBC but then just another of the students pulled in from Sidney Sussex, Cambridge, to work in Hut 6, was on duty in the early hours of 7 May 1944, his twenty-fourth birthday, when one of the most important messages of the war was received. There was no need to decypher it, it was in plain text.
I was working in the Watch on Monday 7 May, my birthday, when I received and passed on to Hut 3 a message in clear from Grand Admiral Dönitz, Commander-in-Chief of the German Navy and Hitler’s successor, saying that Germany had surrendered unconditionally. This was one of many messages in clear received in Hut Six during the last days of the war. I felt that I was participating in history as I received it and passed it on with a mingled sense of excitement and relief.
Stuart Milner-Barry, the head of Hut 6, recalled that the content of the message
was known all over the Hut on the night shift. It is worth recording, I think, that my appeal to all rooms that it should not be passed on to the day shift was honoured in full, and that the first news they had was in the public announcement, after lunch, on the German wireless. That seems to me of its kind to be one of the most remarkable episodes in our history.
The need for utter secrecy had not disappeared with the fall of Germany. With the war against Japan still continuing and a new Cold War with Russia already anticipated, Travis hammered that message home in a ‘special order’ to the staff congratulating them on their work against Germany.
On this historic occasion I want to express my personal thanks to all of you for your loyal cooperation in our common effort to defeat the enemy. The general standards of keenness, discipline, personal behaviour and security have been admirable and have combined to produce a direct and substantial contribution towards winning the war. But our work is by no means ended yet. Three main problems face us now: to finish off the Japanese war; to ease the transition from war to peace conditions as much as possible for everyone; to ensure that nothing we do now shall hinder the efforts of our successors. I cannot stress too strongly the necessity for the maintenance of security. While we were fighting Germany it was vital that the enemy should never know of our activities here. We and our American allies are still at war with Japan, and we are faced with great responsibilities arising out of the preliminaries to peace in Europe. At some future time, we may be called upon again to use the same methods. It is therefore as vital as ever not to relax from the high standard of security that we have hitherto maintained. The temptation now to ‘own up’ to our friends and families as to what our work has been is a very real and natural one. It must be resisted absolutely.
Seven weeks later, on 28 June, the head of the armed forces Field Marshal Sir Alan Brooke visited Bletchley Park to thank the codebreakers for their work. He was accompanied by the First Sea Lord, Admiral of the Fleet Sir Andrew Cunningham, the victor at Matapan. Malcolm Kennedy recorded the event in his diary.
A great day at Bletchley Park, the Combined Chiefs of Staff paying a visit to express their thanks and appreciation of our work. [Air Chief Marshal Sir Arthur] Tedder, unfortunately, was prevented at the last moment from coming, but Sir Alan Brooke and Admiral Cunningham both came, and Brooke made a speech on behalf of all three. It is pleasant to have one’s work recognised in this way by the powers-that-be; and some of the examples he quoted to show how valuable our work had been were of great historical interest although, unfortunately, they are not of a kind that can ever be made public.
The war against Japan continued with Japanese codes and cyphers broken by British codebreakers at Bletchley, in Delhi and in Colombo, until the dropping of the atomic bombs on Hiroshima and Nagasaki in August 1945. Even before the news that an atomic bomb had been dropped on Hiroshima was officially announced, the Japanese messages arriving in Hut 7 at Bletchley Park provided a frightening vision of what had happened. ‘I was on a day watch by myself and all this stuff came in and it was total gibberish,’ said Rosemary Calder. ‘I didn’t know the bomb had been dropped but you could tell from the disruption of all the messages that something terrible had happened. You could just feel the people standing there screaming their heads off.’
Later messages were more specific. An Army-Air message sent to the chief of staff of the General Army Air Command in Tokyo and decyphered at Bletchley Park gave one of the first descriptions of the now familiar mushroom cloud associated with the atomic bomb. ‘There was a blinding flash and a violent blast – over the city centre, the flash and burst were almost simultaneous but in the vicinity of the airfield the blast came two or three seconds later – and a mass of white smoke billowing up into the air.’
Messages decyphered previously by British and US codebreakers had shown that the Japanese would have surrendered before the bombs were dropped if the Allies had been prepared to assure them that the Emperor could remain on the throne. Given that they received this assurance in the subsequent peace deal, it is impossible to comprehend why the horrors of Hiroshima and Nagasaki were inflicted on the Japanese.
Churchill called the codebreakers ‘the geese that laid the golden eggs and never cackled’ and it was not until the mid-1970s that the lifetime ban on them disclosing that they worked there was lifted. Olive Humble was on leave from the Hut 7 Naval Section when Japan surrendered in August 1945.
I came back to Bletchley Park two days later to find all the civilians had shipped out. I was sent to the fearsome Commander Thatcher, who lectured me again about keeping my mouth shut for all time, had to re-sign the Official Secrets Act, and was threatened with the thirty years and or firing squad if I went off the straight and narrow.
But like many of the people who worked at Bletchley Park, Humble had spent the war in what was seen as a ‘cushy billet’ unable to tell even her parents what she was doing.
One thing I regret deeply. I was an only child, on my first day home my father at dinner said: ‘What do you do at the Foreign Office?’ I replied: ‘I cannot tell you sorry, please don’t ask me again’ – and he didn’t, nor did my mother at any time. She died in the early 1960s and he in 1976, before I realised the silence had been lifted.
The contribution made by the codebreakers to the allied victory is truly incalculable. Bletchley Park did not win the war. No single organisation could make that claim. Certainly not of a war that was fought all too often by soldiers killing and dying by the bullet or bayonet. But Bletchley Park’s contribution to the allied victory was enormous. While intelligence was passed intermittently to British officers during the German invasions of Norway and France, and might have helped in small ways, it made no real contribution in either of those campaigns. It was not until late 1940 and the Blitz that Bletchley made its first substantial contribution to the British war effort. The breaking by Hut
6 of the Brown Enigma cypher allowed Bletchley to predict the targets and routes of the Luftwaffe bombers, which ensured that RAF fighter aircraft could ambush them on their way to their targets and that the authorities on the ground could anticipate and prepare for the raids, limiting the numbers of deaths and amount of damage so far as was possible.
The Royal Navy victory over the Italian fleet at Matapan in March 1941 was just one of a number of individual incidents where Bletchley played a direct result in the allied victory. While the extensive knowledge of German intentions in the Balkans that derived from the Ultra intelligence produced by Bletchley did not prevent the German occupation of Greece in mid-1941, it did allow an orderly British withdrawal. Intelligence from Bletchley on German and resistance operations in the Balkans also played a key role in persuading Churchill to back the Yugoslav Partisan leader Tito rather than the Royalist resistance leader Draža Mihailović.
The second half of 1941 saw Hut 8 make the breakthrough on the Dolphin Enigma key used by the U-Boats attacking the trans-Atlantic convoys, allowing the Admiralty’s Operational Intelligence Centre to re-route the convoys around the U-Boat Wolf Packs. Despite the ten-month ‘blackout’ after the German navy introduced the four-wheel Shark Enigma system, the contribution the codebreakers made here was immense. The Battle of the Atlantic is a good example of how Bletchley did not win the war on its own, but it did at numerous points during the war make the difference between success and failure. The U-Boat problems did not stem simply from the fact that the Admiralty knew their locations and intentions. New Allied direction-finding and radar systems became more efficient at tracking them and the US very long-range Liberator aircraft, flown by the RAF in the eastern Atlantic and the Canadians and Americans in the west, ensured that there was no point on the convoy routes where the U-Boats were themselves safe from attack. Nevertheless, as is shown by the horrific losses of merchant shipping when first Dolphin and then Shark were not broken, compared to the much reduced losses once they were being read, Ultra played a critical role in ensuring that Britain continued to receive the vital supplies across the Atlantic.
It was in North Africa where Bletchley Park came into its own, assisted by its outpost in Cairo, the Combined Bureau Middle East. The Enigma decrypts provided vital intelligence in August 1942 ahead of the Battle of Alam Halfa and, from then on, a constant stream of intelligence on Rommel’s vulnerabilities and intentions. British military commanders had until that point seen far less intelligence of value from Bletchley than their naval and RAF equivalents. Now they, and the codebreakers themselves, had tangible evidence of the value it could give in a long-running military campaign. This ensured confidence that the codebreakers could play a critical role in winning the land battle that was to come in the invasion of Europe. It also provided, or should have provided, a number of lessons to commanders not just in how to use Ultra but also in its limitations.
The Mincemeat operation ahead of the Allied invasion of Italy in July 1943 gave an early taste of the usefulness of Ultra in the running and creation of deception operations. The campaign in Italy itself, with the Germans able to use well-established landline communications, provided far less scope for Hut 6 to become heavily involved. But the advent of the Fish teleprinter links and particularly the Bream link between Kesselring’s headquarters and Berlin provided a large amount of intelligence, not all of it limited to operations in Italy.
During the invasion of Europe, Bletchley’s involvement was absolutely vital across the board. The codebreakers’ ability to read the Japanese diplomatic and naval and military attaché cyphers and the Jellyfish encyphered teleprinter link from Paris to Berlin provided the vast bulk of the intelligence on the German defences and allowed Allied planners to ensure that the invasion plans had the greatest chance of success. The breaking of the high-level Abwehr Enigma messages which confirmed that the Germans believed the Double Cross Committee’s deception plan was absolutely critical to the success of the D-Day invasion and also assisted in Operation Crossbow, deflecting the V-weapons attacks on London.
Brigadier Bill Williams, Montgomery’s top intelligence adviser, credited Ultra with providing military commanders with the intelligence that would ensure the victory over the Germans.
Few armies ever went to battle better informed of their enemy. It is recognised by those who ostensibly provided the information that they were but useful hyphens between the real producers at Bletchley Park and the real consumer, the soldier in the field whose life was made that much easier by the product.
At the end of the war in Europe, the Allied commander General Dwight D. Eisenhower wrote to Stewart Menzies, the head of MI6, asking him to pass on his ‘heartfelt admiration and sincere thanks’ to everyone at Bletchley Park ‘for the magnificent services which have been rendered to the Allied cause’. Eisenhower said he was only too aware of the enormous amount of work and effort involved in producing the Ultra intelligence and the setbacks and difficulties the codebreakers had faced down and overcome.
The intelligence which has emanated from you before and during the campaign has been of priceless value to me. It has simplified my task as a commander enormously. It has saved thousands of British and American lives and, in no small way, contributed to the speed with which the enemy was routed and eventually forced to surrender.
The achievements of the British codebreakers against Japanese codes and cyphers have been persistently underplayed. For many years, largely the result of a more lax US approach to releasing historical information, there was a general belief that the Americans broke the Japanese codes and cyphers. In fact we now know that, as with the Enigma and Fish cyphers, the British skill at making the initial breaks into the cyphers was mirrored in the Japanese systems. The Japanese introduced a whole stream of new codes and cyphers in advance of the war. John Tiltman had broken the new Japanese Army super-encyphered codes in 1938 and when the new Japanese Navy General Operational Code was introduced in June 1939, it was broken by Tiltman at Bletchley using material sent back by the British Far East Combined Bureau in Singapore. This was the most important Japanese naval code of the war. Like the Japanese Army codes, it was ‘super-encyphered’ by adding streams of figures to the five-figure code groups.
British codebreakers based in Bletchley, Colombo, Delhi and for a while Kilindini in Kenya made the initial breaks into many of the main Japanese codes and cyphers. But while the British were the ‘break-in’ experts, getting into the codes and cyphers at the outset, the US had a far greater interest in keeping on top of Japanese codes and cyphers, as well as the ability to throw endless amounts of analytical machinery and manpower into the effort. This ensured that the Americans led the way in keeping on top of the Japanese codes and cyphers and therefore produced the great codebreaking coups of the Pacific War like the breaking of the Japanese orders for the Battle of Midway in June 1942, which was critical in the US victory, and the shooting down of the Japanese naval chief Admiral Isoruku Yamamoto in April 1943.
Quite aside from the codebreaking triumphs, there is the simple fact that Bletchley Park was the birthplace of the modern computer. The creation of Colossus was a tremendous achievement and if that was all that had happened at Bletchley Park it would still now be hailed as a demonstration of British brilliance. It is not for nothing that George Steiner, the philosopher and writer, has described Bletchley Park as ‘the single greatest achievement of Britain during 1939-45, perhaps during the [20th] century as a whole.’
So who were the very best of the codebreakers who worked at Bletchley Park? There were in fact so many great men and women working at Bletchley during the Second World War that it is invidious to make such a judgement, but even among the great names four figures do stand out above all the others. These were the truly great codebreakers.
Dilly Knox was a one of the leading experts in breaking hand codes and cyphers on the staff of the First World War codebreaking institution ‘Room 40’ and has never been given the proper credit for his role in
‘breaking in’ to the Zimmermann Telegram. After the First World War, he not only broke the cyphers used by Moscow to talk to its agents around the world, he also decyphered the Mimiambi of the Greek poet and playwright Herodas in his spare time. For most of the 1930s, Knox was probably the only person in British intelligence who believed the German Enigma cyphers could be broken. He broke into the less complex Enigma cypher machines used by Spanish Republican forces and their Italian allies during the Spanish Civil War and it was his ability and understanding of the machine that ensured that the Polish codebreakers felt able to share their own remarkable achievement against the pre-war Wehrmacht Enigma with the British.
Few people in the pre-war GC&CS shared Knox’s confidence that Enigma could be broken. Indeed, Denniston and Admiral Sinclair both believed it an unlikely feat. Without Knox it is likely that the vital wartime breaks into Enigma would have taken far longer to achieve. The breaking of the Abwehr Enigma, a feat deemed too costly in terms of time and manpower by Hut 6 and so abandoned by them, was a fitting climax to Knox’s career, and sixteen months after his untimely death in February 1943 would be a major factor in the success of D-Day. It is even possible that Knox’s work extended still further. In the months before his death, he was working at home on what are believed to have been Soviet high-grade cyphers, so he may even have had an influence on the codebreaking feats of the early Cold War.
The second name in this small group of the very best of the Bletchley codebreakers is John Tiltman, whose experience dated back almost as far as Knox’s – in Tiltman’s case to shortly before the creation of GC&CS in 1919. His ability to break anything from the Double Playfair type systems used by the German police troops carrying out the killings in Eastern Europe to the high-grade machine cypher produced by the Lorenz SZ40 encyphered teleprinter system would set him apart even if he had never broken anything else. Tiltman’s hand is everywhere in the history of Bletchley Park, the first man on either side of the Atlantic to break JN25, the Japanese Navy’s main code system throughout the war, as well as several other main Japanese systems, including the Japanese Military Attaché’s cypher which was to be so productive on the German defences against D-Day. Tiltman was used against any code or cypher that no one else at Bletchley Park could break. His leading role in British codebreaking continued into the Cold War. Although we do not yet know what his full impact was, we know it must have been substantial because he continued to work for Bletchley Park’s Cold War successor GCHQ for a decade beyond the normal civil service retirement age of sixty and even then, at the age of seventy, was recruited by GCHQ’s US counterpart, the National Security Agency, to work for them as a trouble-shooter, yet again dealing with codes and cyphers that no one else could break. He died in Hawaii in 1982.
The Secrets of Station X Page 29