Read The Secrets of Station X Online
Authors: Michael Smith
Two factors prevented the U-Boats from running riot in the North Atlantic in the spring of 1942. First, the Germans did not believe that the three-wheel Enigma could have been broken and were therefore unaware that the introduction of the fourth wheel had left the OIC unable to route the convoys around the Wolf Packs. Second, they had found a new and much easier target. The U-Boats were enjoying their second ‘happy time’ off the eastern seaboard of the United States.
America’s entry into the war in December 1941 had given the Germans the opportunity to attack Allied supply ships at the point where they ought to have been safest, as they travelled along the coast of the United States. The Atlantic was divided into zones in which either the British, Americans, or Canadians had complete control over all naval and merchant shipping. The eastern seaboard was obviously a US-controlled zone. The Americans declined to accept British advice that escorted convoys were safer than individual ships. The US Navy liked the defensive acceptance that some ships would be sunk but more would get through, preferring to send merchant ships along the coast one by one, protected by an offensive programme of routine patrols designed to frighten off the U-Boats.
The result was predictable to all but the Americans. In an operation codenamed
Drumbeat
, the U-Boats simply avoided the patrols, waiting for them to pass before picking off the supply ships one by one. In the first three months of 1942, U-Boats sank 1.25 million tons of shipping off the US east coast, four times the rate they had been achieving in the North Atlantic in 1941. But by mid-1942, a convoy system had finally been put in place, the US Navy had established its own submarine-tracking
room and the Liberty Ships, bigger and faster than the
pre-war
freighters, were being built at a phenomenal rate. Dönitz decided to pull the U-Boats back into the North Atlantic.
It was doubly fortunate for both Bletchley Park and the British that they had not been there when
Shark
was first introduced, said Harry Hinsley. Not only would the number of Atlantic convoys successfully attacked have been much greater during this period but the Germans might have realised that the three-wheel Enigma had indeed been broken.
Had the U-Boats continued to give priority to attacks on [North] Atlantic convoys after the Enigma had changed, there would have been such an improvement in their
performance
against convoys that the U-Boat command might have concluded that earlier difficulties had been due to the fact that the three-wheel Enigma was insecure.
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 read 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.