The OIC was not totally blind as to the presence of U-Boats in the North Atlantic. Details of new submarines being built and tested in the Baltic could be had from Dolphin, which continued to be used in Norwegian and Baltic waters, and from the medium-grade Dockyard cypher. Bletchley Park usually knew when a U-Boat was leaving the Baltic or the Bay of Biscay on an operational cruise and when it was coming back. But once the U-Boats were in the Atlantic, the only indications of what was going on came from direction-finding and radio-fingerprinting techniques, and knowledge of the U-Boats’ typical behaviour, capabilities and endurance, none of which were reliable.
The Wolf Packs resumed their attacks on the Atlantic convoys in August 1942 with eighty-six U-Boats, four times as many as when Shark was introduced. One of the first attacks came over five days between August 5 and 10 when the Gruppe Steinbrinck Wolf Pack of eighteen U-Boats attacked a convoy of thirty-three Allied ships, sinking eleven, a total of 53,000 tons of shipping.
During August and September 1942, the U-Boats located twenty-one of the sixty-three convoys that sailed, sinking forty-three ships. They destroyed 485,413 tons of shipping in September, and in October, when there were more than a hundred U-Boats at sea, sank 619,417 tons, the first time they had destroyed more than 500,000 tons of merchant shipping in a month. At the same time, the number of U-Boats sunk dropped to just five in August and three in September. It rose to eight in October but, by the third week of November, only two U-Boats had been sunk while the number of Allied ships lost that month was rising steadily toward the one hundred mark.
The Admiralty began to step up the pressure on Bletchley Park to break Shark. The OIC urged Hut 8 to pay ‘a little more attention’ to the U-Boat cypher. In a tersely written memorandum, it complained that the U-Boat campaign was ‘the only one campaign which Bletchley Park are not at present influencing to any marked extent and it is the only one in which the war can be lost unless BP do help’.
There was no need to push the codebreakers any harder than they were pushing themselves. Turing and Alexander were obsessed with the Shark problem, to the detriment of security, as John Herivel recalled.
I was standing on the platform at Bletchley station one day. Alexander and Turing were standing, not all that close, and I could hear them talking at what seemed to me to be the tops of their voices about some matter in connection with Bletchley Park. But it was a cryptographical matter. So they were probably quite safe because no one would have known what they were talking about. On the other hand, if there had been an intelligent German spy on the platform, he might have twigged that it was something to do with cryptography.
Although Turing was in theory head of Hut 8, he spent a great deal of 1942 working on other matters. The hut was effectively run by Alexander but without the full authority that he would have had as head of the hut. Following the OIC’s complaint, Alexander was put in charge of Hut 8. One of his first acts was to institute daily ‘U-Boat meetings’ with the Naval Section. He also increased pressure for the introduction of the new Bombes designed to cope with the four-wheel Enigma machine.
But the solution to Shark was already in place. Two days after the Admiralty memorandum, a pinch of two German ‘short signal’ codebooks arrived at Bletchley providing new cribs for the U-Boat messages. The books had been recovered from the U-559, which had been scuttled by its crew after being attacked by the British destroyer HMS Petard off the Egyptian coast on 30 October 1942. The Petard’s first officer, Lieutenant Anthony Fasson, and Able-Seaman Colin Grazier swam to the submarine before it sank and managed to recover its signal documents. They were joined by a sixteen-year-old Naafi boy, Tommy Brown, who had lied about his age to get on active service. He succeeded in getting out with the codebooks, but Fasson and Grazier went down with the submarine. They were both awarded the George Cross posthumously. Brown, a civilian, received the George Medal. The medals were well-deserved; their heroism was vital in helping to end the U-Boat blackout.
The documents that they had rescued from the U-559 included the current Wetterkurzschlüssel, the Short Weather Signals codebook, and the Kurzsignalheft, the U-Boats’ short signal book which was used to report locations of Allied convoys. These would provide Hut 8 with the cribs they needed to break into Shark. The two codebooks arrived at Bletchley on 24 November and the Hut 8 codebreakers decided immediately to put all their efforts into breaking Shark, Shaun Wylie recalled.
We knew that we had a good chance and we certainly put a tremendous amount of effort into it, Bombe time and all that sort of thing. Looking back on it I think we might have chanced our arm and hoped to be lucky, but we did decide to give it everything.
One vital flaw with the Shark machine offered the codebreakers hope of breaking it now they had access to cribs from the Wetterkurzschlüssel and the Kurzsignalheft. When the U-Boats communicated with the shore weather stations they had to use the three-wheel set-up, making the keys for the first three wheels relatively easy to break. Once they were broken there were only twenty-six options to try out on all the other messages to find out the setting of the fourth wheel. ‘We found that certain types of signals still used three wheels,’ Noskwith noted. ‘These were certain short signals and weather signals from U-Boats. The time when we found these short signals was a very exciting time.’
Wylie took over the codebreaking shift in Hut 8 at midnight on Saturday 12 December. All night they continued the tedious process of looking for cribs from Hut 10’s weather reports that might fit the short U-Boat weather messages. Wylie was in the canteen the next morning when one of his colleagues came running in. They had found a Shark message with the fourth wheel in the position that allowed it to operate as a three-wheel Enigma. A Bombe menu was constructed on the basis of a potential crib from the Short Weather Signals. It was tried out on six Bombes and the crib came out.
‘I was having breakfast and somebody rushed in and said: “We’re back into the U-Boats,”’ Wylie recalled.
I asked which it was and it was the one that meant we were going to be able to go on getting into the U-Boat traffic. That was terrific, it wasn’t just a one-off. We were going to be able to do it steadily. It was a great moment. The excitement was terrific, relief too.
Once Wylie had checked it out, he was under instructions to inform Travis immediately. There were celebrations in the Hut and at the Admiralty. ‘We were elated,’ Wylie said.
We knew that from then on we had good prospects of keeping in with it. We knew we were in with a chance. I was told to ring up the boss as soon as it came in and Travis was going to ring up Menzies who would ring Churchill.
Within a few hours, Hut 8 had broken the day’s keys and decyphered messages began to arrive in the Submarine Tracking Room where Lieutenant Patrick Beesly was on duty. ‘They continued to do so in an unending stream until the early hours of the following morning,’ he said. ‘It was an exciting and exhausting night.’
Pat Wright was one of the young women working in the Big Room at Hut 8, decyphering the messages. She had been recruited earlier that year.
I was just approaching my eighteenth birthday. I had a letter at home asking me if I would go for an interview at the Foreign Office. There were several other girls there. They told us they wanted us to do something but they couldn’t tell us what it was and that we would be hearing from them. So I went home and my mother said: ‘What did they want you for?’ and I replied: ‘Well, I haven’t the faintest idea.’ Eventually we received a letter and train passes to go to Bletchley. We were taken to the big house and were lectured by a very ferocious-looking security officer and we signed the Official Secrets Act. They said: ‘The job we want you to do is decoding.’ Well, everybody knows the Foreign Office has codes. It didn’t seem very secret. We trailed over to Hut 8 where they said: ‘Well, the thing is it’s German naval codes, we’ve broken the codes and we want you to do the decoding’ – collapse of several young ladies in a heap. None of us were fluent German speakers.
It was then rea
d out to us in no uncertain terms that on no account were we to tell anybody what we were doing. Nor were we to say we were on secret work. It wasn’t secret. We were the evacuated office of the Foreign Office and we were copy typists. It was explained to us that the German codes had been broken by this super machine that had been invented. At the same time every day, the Germans transmitted this weather message beginning exactly the same way. This was of course not anything that we lesser mortals had to worry about. This was the brainy boys’ department.
The ‘copy typists’ in the Big Room operated Type-X machines decyphering the messages that came in. They had to wait for the codebreakers to break the keys first.
Sometimes we had to wait a long time. Sometimes it was done quickly. But there was always a backlog of work, so we were never not having to do anything. There were four wheels out of a box of eight which were put into the machine and then turned to the right letter of the alphabet and then there was a plugboard with plug leads that went everywhere. You started off typing and then with a bit of luck you suddenly saw something you could recognise as German. There were of course very clever interpreters there who, if you got into a real fix, where the German went off into garble, would help you, because not many of the messages were wholly intercepted. Bits were missing or not picked up. So it wasn’t a case of just typing straight through. Anybody who works a computer now that has this light touch would be horrified. The keys had to be pressed right down and came up with a clankety bang. It was very, very noisy. It printed out on to a long strip of sticky tape a bit like you used to get on old-fashioned telegrams.
When we finished we took the message and stuck it on the back like an old telegram. Then we would send it through and says: ‘Shall we go on with this?’ and they would say: ‘Yes, keep going,’ or ‘No, don’t bother.’
She and the other women working in the Big Room were well aware of the importance of what they were doing.
Clothing was rationed, soap was rationed, sweets were rationed, and the Atlantic convoys coming across were being sunk quicker than they could take up with thousands of men and we were just told that if they could just keep these messages decoded then they would keep the submarines away from the convoys.
One of those working in Hut 4 was Sarah Norton, who had been promoted from the index to translating German decrypts. She remembered the time of the blackout as a very depressing period.
It was a terrible, terrible time because all our shipping was going. We could have starved, actually, and eventually when they broke it the volume of work was just unbelievable because every signal had to be translated. It might just be a floating mine. It might have been something terribly important like a U-Boat attack somewhere. So it all had to be done and we had to work extremely hard.
A new canteen capable of coping with 1,000 people at a single sitting was completed in the spring of 1942 and the builders began work on the larger concrete blocks which would replace the wooden huts. Throughout 1942, wave after wave of new recruits arrived at Bletchley and as the new purpose-built blocks were finished, in the latter half of 1942 and early part of 1943, there was a mass exodus into the new accommodation, although for security reasons the Hut numbers remained the titles of the various sections. The decyphered messages were sent to Z Watch in Hut 4 via Lampson Tubes, vacuum tubes that distributed papers around the Park and were known to the young girls who used them as the ‘spit and suck’.
‘We moved from Hut 4 which we loved into a horrible concrete building,’ said Sarah Norton, one of the debutantes working in the naval index.
To be totally perverse, we insisted on still calling the new block Hut 4. It had a long wide corridor which ended in a T-junction. One afternoon, we decided to give Jean Campbell-Harris, who later became Baroness Trumpington, a ride in a large laundry basket on wheels that was normally used to move secret files. We launched it down the long corridor where it gathered momentum by the second. To our horror, at the T-junction, Jean suddenly disappeared, basket and all, through some double swing doors crashing to a halt in the men’s toilets. A serious reprimand was administered and our watches were changed so we were distributed among a more sober group. But this fortunately did not last long.
Their efforts were rewarded with a dramatic drop in the number of successful U-Boat attacks. But when Shark was lost in early March, following the introduction of a new short weather code, it looked as if a new blackout had begun. But by concentrating the increasing number of Bombes on the problem, and with the assistance of the first ‘Keen Machine’, Hut 8 broke the keys out within ten days.
From that point on, the new-found confidence in Hut 8 and the introduction of the much faster US four-wheel Bombes produced by the National Cash Register (NCR) company in Dayton, Ohio, ensured that Naval Enigma was never as difficult to break again. Relations with Op-20-G were now on a much firmer footing with all the old concerns and complaints removed by the joint interest in cooperating fully to protect the Atlantic convoys. Travis flew to America in October 1942 to meet Capt Carl F. Holden, the US Navy’s Director of Communications. They signed the so-called Holden Understanding, which committed both sides to cooperation on the breaking of the German naval cyphers, and in particular Shark. The daily keys and any messages that were broken were sent across the Atlantic on US bombers in what became known as ‘the Bomber bag’.
Joe Eachus, the US Navy liaison officer, began working in Hut 8 as a naval codebreaker.
My official duty was to report back to Washington what was happening at BP. But that was not a full-time job, so I undertook to be a cryptanalyst while I was there. It had been a hobby of mine before the war. Some of the British had been in the FO as professional codebreakers for some years, but there were no US Navy guys who fitted that description. Everybody had been amateurs before. We were working on German Enigma and often-times we were reading stuff currently. Other times, something would happen and we were not and there was just a feeling of gloom around when we would go for a week without reading things, very downhearted. Then it got going again and you would see the smiles in the corridors. That was very noticeable that people there took a personal interest in the work. As an officer I was permitted to circulate a good deal more than most of the people who worked there, I had a good excuse, and there were a lot of academics there, particularly from Cambridge. I met professorial types on an equal footing in a way I would never have otherwise done. They were always a level or two above me. I found their attitude towards life very interesting. They were academics primarily and their personal life was secondary. My view had always been the other way round, my personal life was the primary thing and my professional life was a way of making a living.
The Americans became so adept at breaking Shark, largely due to the enormous number of four-wheel Bombes they built, that by the middle of 1944, with Bletchley fully involved in providing intelligence on the invasion of Europe, and with the British four-wheel Bombes incapable of matching the reliability of their American counterparts, the US Navy codebreaking organisation Op-20-G had completely taken over responsibility for breaking Shark. The US Navy Bombes were even used to run menus for Hut 6 during the invasion of Europe, so good had relations between Op-20-G and Bletchley become. ‘In all they produced well over 100 machines which were of the utmost value to us, not only on Naval keys but also in Air and Army,’ Alexander said.
Indeed considerably more than half the total American Bombe time went on non-naval keys. Their whole hearted cooperation and readiness to use their Bombes for jobs in which they, as an organisation, had no direct interest was always very greatly appreciated by us; a great deal of our success on all keys (Naval, Air and Army) in the last two years of the war was due to their help.
The Allies had been lucky that Dönitz had chosen to concentrate on the eastern seaboard of America for the first part of 1942, Frank Birch said. If he had not, the U-Boats might well have pushed Britain to the brink of starvation.
The only comforting thought about those ten mont
hs is that at the time British resources were so meagre that even with all the information in the world only moderate immunity could have been obtained. By March 1943, when Special Intelligence was coming along strong, though not yet at full strength, the Germans had become incapable of reading our stuff and in the great showdown of that month the U-Boats were, as a result of Special Intelligence, driven off the convoy routes for six months.
The break into Shark was not the only deciding factor in the Second Battle of the Atlantic; the introduction of the Very Long Range Liberator aircraft, centimetric radar, the Huff-Duff shipborne DF system and new naval support groups, including aircraft carriers, made life altogether too dangerous for the U-Boats. But it was the ability to read the U-Boat messages that allowed the Allies to use these new-found resources to conduct a war of attrition against them, trading the loss of merchant ships for the destruction of a U-Boat, Beesly recalled.
Decisions had to be taken, never lightly, never without due thought, but taken none the less and one had to accept the consequences. We were far removed from the sea but it did not require a great deal of imagination to picture tankers going up in flames, seamen being drowned or maimed, or invaluable cargoes being lost. The only possible way to treat the matter was as though it were a game of chess. Ships or U-Boats were pawns. When one of them was sunk it was removed from the board. One side or the other had gained a point, but the game was not over and one had to turn immediately to consider the next move, to try to save the remainder of one’s pieces and to take out some of one’s opponents.
The Secrets of Station X Page 19