The eclectic mix of people based at Station X was an eye-opener for many of the young men and women who found themselves there. Diana Russell Clarke had the time of her life at Bletchley Park.
We all had a marvellous time, all these young men, not attached. We had a very gay time going out to pubs for supper together when we were free. A lot of romance went on, very definitely a lot of romance. The whole thing was absolutely tremendous fun. It’s rather awful in the middle of the war. We had to be there, it was an emergency and I think we all put our hearts into it. But I think we all enjoyed being there.
The increasing success of Bletchley Park in producing vital intelligence, not just from Enigma but also from Oshima’s highly detailed messages from Berlin to Tokyo and from lower level naval and Luftwaffe codes and cyphers, led to a power struggle within Hut 3 for control of the Ultra intelligence reports. The number of Enigma messages had grown from fifty decrypts a day when Hut 3 was first set up to 1,300 a day, making them increasingly important to the service departments and a source of influence that some within MI6 wanted to use for their own purposes. The advisers provided by the Military and Air Sections of MI6 tried to take control of the Hut 3 reporting. The attempted coup was led by Squadron-Leader Robert Humphreys, who had been put into Hut 3 by Frederick Winterbottom, the head of Section IV, the Air Section of MI6. Lucas recalled:
Humphreys had the highest technical qualifications through his real mastery both of intelligence and of German, but unfortunately he aimed at securing control over the organisation for himself. Moreover, he tried to set up within Hut 3 a semi-independent and almost rival organisation responsible to himself. It cannot be doubted that he made a great contribution to our work and also to getting it taken seriously at the highest levels. Nevertheless, he caused great dissension and disturbance.
An attempt to resolve the situation by giving the military and air advisers a veto over both the circulation of the reports and their content only increased the problems and resulted in an ‘imbroglio of conflicting jealousies, intrigue and differing opinions’, Nigel de Grey said. The atmosphere in the hut became ‘tense and unpleasant’ and, with the standard of output being affected, Menzies himself was forced to intervene on a number of occasions. No doubt influenced in part by this and in part by the discontent that had led to the joint letter to Churchill, Menzies decided that Denniston, who had been unwell, was not the right man to control such a rapidly growing organisation. An inquiry put in place by Menzies recommended splitting the organisation in two, with Denniston becoming Deputy Director (Civilian) and limiting his control to the diplomatic and commercial sections, which were to move to London – with the exception of Foss’s Purple section – while the sections handling German, Italian or Japanese military, air or naval intelligence remained at Bletchley under the control of Travis who was to become Deputy Director (Services). Nigel de Grey was appointed Assistant Director (Services) effectively making him Travis’s deputy and Tiltman was made Chief Cryptographer, replacing Dilly Knox who by now was seriously ill with cancer. Denniston was privately ‘very bitter’ about the way he had been manoeuvred out of control, but took it very well. He moved to very good accommodation in London in March 1942, with the diplomatic sections based in Berkeley St and the commercial sections in Alford House in Park Lane. Change was inevitable, Ralph Bennett said.
Denniston had spent his life in the time of the Battle of Hastings dealing with hand codes and not much information that you could use militarily. Then he found himself in charge of a huge growing organisation, a lot of us younger and in some ways thinking along different lines, and he got a bit outdated in some ways and was shunted out. It was a bit of bad luck on him because he was a very good chap but he was overtaken by events.
The rows within Hut 3 were removed by putting Squadron-Leader Eric Jones, an air intelligence officer who had taken part in the inquiry, in charge. Jones, a future post-war head of GCHQ, removed all the tension by dint of good man-management.
‘There was an inter-service rivalry there and [people] jockeying for position,’ said Jim Rose, one of the Hut 3 intelligence officers.
Jones was just ideal. He had left school at fourteen and had been in the cotton business in Manchester. He was very intelligent, didn’t know German but understood organisation very well. He gave people a free hand. It all became crystal clear. Quite a lot of brainy people had the habit of resigning when they were miffed. We used to keep a graph of when we expected one or two of them to resign but Jones dealt with them.
Jones augmented the Hut 3 system with a team of Duty Officers who would lead each shift, effectively replacing the Watch Number Ones. ‘Under his firm but understanding rule, we could concentrate on our work undisturbed by internal conflict,’ said Ralph Bennett, who was one of the newly appointed Duty Officers.
The watch received the raw decoded messages straight from Hut 6 with all the corruptions and they translated it into English. Then the translations went to either the air or the Army desk to be put into military sense. These chaps passed it to the duty officer for final vetting and for checking for security. No signal could go out of Hut 3 without the initials of the duty officer.
Bletchley Park’s early successes against the U-Boats in the Battle of the Atlantic and the ease with which the Allied shipping convoys were evading the Wolf Packs had led Admiral Karl Dönitz, the admiral in charge of the German U-Boats, to suspect that something was very wrong. Either the British had a very good intelligence network in western France and had managed to infiltrate the U-Boat control system or Enigma had been broken. Dönitz ordered the German codebreakers to look at the Enigma system themselves and demanded to know for sure, was it really impregnable?
‘We found ourselves bound to admit that we had not succeeded in finding with our reconnaissance sweeps the convoys for which we had been searching,’ Dönitz recalled.
As a result of these failures, we naturally went once more very closely into the question of what knowledge the enemy could possibly have of our U-Boat dispositions. Our cyphers were checked and re-checked to make sure they were unbreakable and on each occasion the head of the naval intelligence service adhered to his opinion that it would be impossible to decypher them.
Nevertheless, when Dönitz was given a chance to make the submarine cypher even more secure he jumped at it. The plan involved a slight internal re-design of the Enigma machine. A new, thinner reflector with different wiring was introduced, leaving space for an extra wheel that, while it did not rotate during encypherment, could be set to different positions, adding a further factor of twenty-six to the number of possible solutions. The German cypher experts were convinced that it would now be impossible for anyone to break.
The first sign of the fourth wheel came in early 1941, in a captured document. In August of that year the U-570 surfaced south of Iceland only to find that a British Hudson patrol aircraft was directly above her. The pilot, Squadron-Leader J. H. Thompson, dropped four depth charges, two on either side of the U-Boat, causing so much damage that the commander was forced to surrender. Inside the U-Boat was the casing of an Enigma machine with a fourth indicator window.
References to the fourth wheel soon started to appear in decyphered messages and, on occasions, operators used it in error. When the Germans had designed the fourth wheel they had taken into account the fact that anyone using it might have to talk to other stations equipped with only the three-wheel machine. So in one of its twenty-six positions it replicated the action of the old reflector, turning the four-wheel machine into the equivalent of a three-wheel machine. By the end of the year, the wiring of the wheel had been recovered from a number of messages sent first using the fourth wheel and then, after the other operator pointed out the mistake, with just three wheels.
On 1 February 1942, the U-Boats introduced the fourth wheel, creating a new cypher dubbed Shark by the Bletchley Park codebreakers. Patrick Mahon, one of the Hut 8 codebreakers, and later the head of Hut 8, recalled:
T
his was a depressing period for us as clearly we had lost the most valuable part of the traffic and no form of cryptographic attack was available to us. The effect of a fourth wheel was to multiply by twenty-six the number of possible positions of the machine for each wheel order and also to make Banburismus out of the question. To have obtained sufficient depth on this much improved machine an approximate equivalent increase of traffic would have been necessary.
Hugh Alexander, Turing’s deputy and effectively, given Turing’s complete lack of interest in administration, the de facto head of Hut 8, recalled the next nine months as ‘a rather gloomy period’ in the Hut’s history.
‘The change meant that we had to break it quite independently of Dolphin,’ Alexander said. To make matters worse
breaking on three-wheel Bombes would be so extremely laborious that unless there was a steady stream of absolutely first class cribs our existing Bombe resources would be quite inadequate. Even given this stream so much Bombe time would be used that the Air and Army keys would suffer very seriously; an average Shark job would have taken 50 to 100 times as long as an average Air or Army job so that it would have been a moot point whether it would have been worthwhile even if possible.
While they could continue to break Dolphin, which was still being used in the waters of Norway and in the Baltic, they were now unable to do anything with Shark. The vital intelligence the Admiralty’s Operational Intelligence Centre (OIC) had been using to re-route the Atlantic convoys had disappeared.
‘We were dismayed when the fourth wheel appeared,’ said Shaun Wylie, the head of the Hut 8 Crib Section.
We knew it was coming. But it was a grim time. We were very much frustrated; the things that we’d hoped to use went bad on us. We realised that our work meant lives and it ceased to be fun. We did what we could, of course, and we got on with what there was, but we kept an eye out for any possibility on Shark that might present itself. There was a lot of pressure and we were trying all we could but we didn’t have many opportunities. We had to get Dolphin out, but Shark was the prime target, the focus of our interest.
The problems caused by the ‘Shark blackout’ were exacerbated by an increase in the number of U-Boats in the Atlantic to forty and by the breaking by the B-Dienst – the German equivalent of Bletchley Park – of the Royal Navy’s Naval Cypher No. 3, which was used for most of the Allied communications about the Atlantic convoys. A week after Shark came into force, the OIC’s submarine tracking room admitted that it was at a loss to say where the U-Boats were. ‘Since the end of January, no Special Information has been available about any U-Boats other than those controlled by Admiral Norway,’ it reported. ‘Inevitably the picture of the Atlantic dispositions is by now out of focus and little can be said with confidence in estimating the present and future movement of the U-Boats.’ A break into Shark was desperately needed if the Wolf Packs were not to be given a completely free hand in the North Atlantic.
With a great deal of work, Hut 8 did manage to solve the keys for two days in late February and one day in March. But it took six of the Bombes seventeen days to solve each of those settings. Noskwith recalled that there was a feeling of deep disappointment but while the codebreakers were doing everything they could to solve Shark, ‘there was an acceptance of the fact that until we had better Bombes, faster Bombes that could work through the twenty-six times as many permutations, we wouldn’t really be able to cope with it’.
The Bombe section had been further expanded with the addition of a new outstation at Stanmore, in Middlesex; increased recruitment of Wrens; and two different development programmes put in place to produce an upgraded Bombe that could cope with the four-wheel Enigma machine. Doc Keen began work on a high-speed machine with an additional row of wheels that could complete a standard three-wheel run in less than two minutes. But the first experimental ‘Keen Machine’ could not be produced before March 1943.
The other development program was led by Dr Charles Wynn-Williams of the Telecommunications Research Establishment at Malvern, where a team of GPO engineers had started working on a high-speed Bombe. This had a long snake-like attachment to replicate the fourth wheel which led to it being called Cobra. But it could not be brought into operation until early 1943.
The codebreakers’ acceptance that their best chance of breaking Shark was through bigger and better Bombes led to further conflict with the OIC which, as one naval intelligence officer recalled, was unable to look at the problem with such scientific detachment.
There was a danger of BP’s researches being too academic. Their researches though brilliantly conducted were more like a game of chess or the arrangement of the jigsaw puzzle. They set the known against the unknown and proceeded to a dispassionate consideration of deductions. We saw the problem in a different light, for us the merchantmen and motor torpedo boats, the patrol vessels, and the Sperrbrecher [specially reinforced escort vessels] lived and moved and had their being in a world vibrant with the noise of battle. It was almost as though with a finger on the enemy pulse we brought a warmth and a sense of reality to our research work which was noticeably lacking from many similar efforts by BP.
The concerns were understandable. A total of 2,452 Allied merchant ships were sunk by the Germans in the Atlantic with more than 30,000 members of the British Merchant Navy killed in often horrific circumstances. Sailors floundering in their life jackets after a U-Boat hit could not be rescued because to do so would put the ship taking them on board at too much risk of being sunk itself. ‘I saw it first in HMS Alaunia in 1940,’ recalled one sailor, whose ship was passing within feet of men who were floating in the water after surviving the sinking of their ship.
They shout, even cheer, as you approach. The red lights of their life jackets flicker when they are on the crest of a wave and are doused as they slip into the trough. Their cries turn to incredulous despair as you glide by, unheeding, keeping a stoical face as best you can. But the cold logic of war is that these men in the water belong to a ship that has bought it and that a couple of dozen more ships survive and must be protected. Each time was as bad as the first. We never got used to it.
Faced with such tragedy, the logic of the Hut 8 codebreakers must certainly have seemed far removed from reality to the naval officers and other ranks working in the OIC, but just like the orders to the ships in the convoys that they must not stop to pick up sailors, it was the only sensible and logical approach to take.
‘I have been asked whether our prolonged inability to break Shark gave us a sense of guilt,’ Noskwith said.
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 breaking the four-wheel machines. Thirdly, we were still regularly breaking Dolphin 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 breaking a crucial day while the Arctic convoy PQ17 was being slaughtered by U-Boats and aircraft.
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 Secrets of Station X Page 18