Blackett's War (39 page)

The trouble was that British electrical and mechanical engineering was turning out to be unequal to British mathematical genius. To work through every possible combination of four rotors in a reasonable amount of time required the fastest wheel to spin at a dizzying 2,000 rpm. The engineers of the British Tabulating Machine Company had barely managed to get the electrical contacts on their three-rotor machines to work reliably at speeds of under 100 rpm. Work had been dragging for months on the new four-rotor bombes, and was getting nowhere.
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By the summer of 1942, the U.S. Navy’s cryptanalytical unit (known only by its bureaucratic designation in the navy command structure, Op-20-G) concluded that what was clearly needed was a dose of good old American know-how, and shocked their British colleagues with the pronouncement that they were going to enlist American industry to build a few hundred of their own four-rotor machines to get the job done. British secret service officials fought a feeble rearguard action for a few weeks, then threw in their hand. Faced with the inevitable, Edward Travis, who had succeeded Denniston as Bletchley’s director following the prime minister’s
ACTION THIS DAY
directive, and Frank Birch, head of the naval section, departed for Washington in September to negotiate a formal agreement for “full collaboration” between GC&CS and the U.S. Navy on the naval Enigma problem. Later that fall the U.S. Navy signed a $2 million contract with National Cash Register to build the four-rotor bombes at its Dayton, Ohio, plant. In the end, NCR, assisted by 600 WAVES who were dispatched to Dayton, would build 125 of the machines at twice that total cost.
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None of this solved the immediate problem. The new machines could not possibly be ready before spring 1943, and the pressures for action were mounting daily. November 1942 saw the greatest monthly sinking of Allied merchant shipping by U-boats of the entire war, more than 800,000 tons. Churchill convened a new Cabinet Anti-U-boat Warfare Committee and began his usual hectoring from on high. On November 22, the Admiralty’s Operational Intelligence Centre added a circumspectly worded but urgent plea, asking the GC&CS naval section if “a little more attention” might be paid to the naval Enigma problem.
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Two days later a pile of documents landed at Bletchley Park like a deus ex machina.

Since the beginning of the blackout of the U-boat traffic in February 1942, Alan Turing and the other Bletchley mathematicians assigned to the naval Enigma problem had been trying to devise a way to break back into the system even without a four-rotor bombe. Through another feat of
pure mathematical analysis, they quickly determined that the four-rotor machines had been designed to be compatible with the existing three-wheel Enigmas so that the U-boats could continue to communicate with networks that had not been issued the more secure version. When the fourth rotor was set to the “A” position, the machine acted exactly like a three-rotor machine. What was more, certain kinds of short signals were routinely sent by the U-boats with the fourth rotor set to this “neutral” position. These were mainly weather reports, which were encoded by a series of letters of the alphabet according to a printed weather codebook before being enciphered on the Enigma and radioed.
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The other promising discovery the Bletchley naval staff made was that the U-boat weather reports were regularly retransmitted for the benefit of the entire German navy by a powerful transmitter at Norddeich, on the North Sea coast, using a simple code that Bletchley had already broken. It was generally an easy matter to match up a Norddeich weather report with the U-boat Enigma message that had provided it; one clue was that the weather short-signal code allowed latitude and longitude and wind speeds to be specified only in round figures, so any Norddeich report containing wind speeds divisible by four or latitudes and longitudes given to a whole degree had almost surely come from a U-boat.
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All that Bletchley needed now was the weather codebooks themselves to be able to construct a three-rotor bombe crib that it could solve with its existing methods. Having already mathematically reconstructed the internal wiring of the fourth rotor by analyzing the signal traffic, they would then be able to read all the U-boat traffic directly.

On October 29, 1942, a British patrol in the Mediterranean spotted a surfaced U-boat halfway between Port Said and Haifa, and four destroyers were ordered to head for the spot. Shortly after noon they made sonar contact, and for the next ten hours the warships waged a relentless depth charge attack against their hiding prey. The last salvo ripped a hole in the bow of the submarine, sending it hurtling to the surface and ending the fight. Survivors told British interrogators that they had counted 288 explosions as they lay beneath the surface.

Within minutes of breaking the surface,
U-559
was being boarded by three sailors from HMS
Petard
who had leapt into the water and swum across. With water already rising belowdecks, the three began grabbing armfuls of documents from the control room and captain’s berth and carrying them up the ladder to pass to another boarding party that had meanwhile
arrived alongside in a whaleboat. One of the officers had just ordered the men to come up at once when the U-boat suddenly plunged beneath the surface. Tommy Brown, a sixteen-year-old canteen assistant who had lied about his age to join the navy, was just able to jump free in time and avoid being pulled under by the eddying undertow of the diving U-boat. Able Seaman Colin Grazier and Lieutenant Anthony Fasson were carried down to their deaths. Brown was presented a medal—and a discharge from the navy for being underage.
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It was grudging recognition considering his act helped win the entire Battle of the Atlantic. Among the documents Brown and the others managed to rescue was the latest weather codebook and a list of Enigma settings used to transmit the short signals. After running the bombes for two weeks straight, Bletchley sent a teleprinted message to the Admiralty early on the afternoon of December 14 giving the positions of a dozen U-boats in the Atlantic. At 9:00 p.m. the day after Christmas the code breakers read the first current day’s U-boat messages in almost a year. Some 39,000 U-boat decrypts would follow to the end of the war. The December 26 break came just hours too late, however, to save convoy ON 154, which had been located by a U-boat that same afternoon. Two days later a wolf pack sank nineteen freighters and two escorts in the convoy.
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But over the next two weeks Dönitz’s U-boats in the Atlantic were unable to locate a single one of eight “expected convoys” that BdU had alerted them to based on the B-dienst’s decodes of Allied convoy signals. Every one was successfully diverted around the waiting wolf packs. Moreover, the signals exchanged between the U-boats and BdU that were required to organize a wolf-pack attack, and which were now being read by Bletchley Park, frequently gave Coastal Command time to dispatch one of its small number of VLR aircraft on the 1,000-mile journey to protect a convoy before the attack could be mounted. There was, Blackett noted, “almost never less than twelve hours and seldom less than a day” of advance warning that an attack was imminent. The Enigma intelligence was a literal force multiplier, allowing the still severely limited VLR force to become forty times more effective than it otherwise would have been: Blackett calculated that a VLR aircraft sent out to intercept a convoy known to be shadowed by a U-boat successfully sighted a U-boat 1 time in 2.4 sorties, versus 1 in 100 when simply assigned to escort a convoy as a general defensive measure.
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Once again puzzling over the curious elusiveness of the convoys, Dönitz ordered a full-scale security investigation. There were now only two possibilities,
he noted in his war diary: “(a) that the enemy has succeeded in temporarily breaking into our cipher data or (b) that in some place or other in our own ranks there is treason.” The answer was staring him in the face. Investigators from the Naval Communications Service in Berlin combed through the signals the British and Americans were radioing their convoys and found several that should have rung alarm bells. On repeated occasions convoys had been sent signals ordering them to change course to evade U-boat patrol lines or correctly reporting the locations of U-boats with an accuracy that surpassed what should have been possible by radio direction finding alone. One report had accurately noted the presence of twenty U-boats in the area; how could the British possibly have known the exact number from direction-finding fixes? Still another Allied signal had reported that two U-boats were at 31° N, 39° W for a possible rendezvous with a supply ship. That was fine: except that the rendezvous, ordered by a radio signal sent to the boats by BdU, had not yet taken place.

Incredibly, the investigators shrugged off all the evidence that their enemies were reading the Enigma traffic. The clinching argument, in their view, was that if the British possessed the cryptological genius required to penetrate the complexities of the Enigma, they would surely not have made such a simple-minded mistake as to use an insecure code like the Naval Cypher No. 3 for their own vital communications.
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Meanwhile, everyone in the U-boat command structure with access to operational orders and signals was interrogated and placed under surveillance. Only Dönitz and his chief of staff, Kapitän zur See Eberhard Godt, were considered exempt from suspicion. When this avenue also failed to turn up any source of the leaks, Godt made a small joke. “Shall I investigate you,” he asked his commander-in-chief, “or will you investigate me?”
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TWO SQUADRONS OF
U.S. Army Air Forces B-24 Liberators at Langley Field, Virginia, were the first Allied submarine-hunting aircraft to receive the new centimeter-wave radars, and on November 6, 1942, the first three aircraft of the group took off from Gander, Newfoundland, for the difficult transatlantic crossing. Flying across the ocean was still an intrepid undertaking in 1942. There were no radio beacons or reliable weather data over much of the Atlantic; like mariners in the age of sail, aircraft navigators relied on celestial fixes with sextants to establish their location and more than a little seat-of-the-pants experience to avoid dangerous weather. Over
the next several weeks two of the Liberators from the 1st and 2nd Antisubmarine Squadrons vanished while making the attempt to cross the Atlantic and were never heard from again.

Adding to the perils of weather was the usual comedy-of-the-absurd snafus of military bureaucracy. The squadrons were originally intended to join the Allied forces that had landed in North Africa that month, and to operate out of bases in French Morocco. The decision was then made instead to attach them, at least temporarily, to Costal Command in England while they gained experience operating their new equipment patrolling the Bay of Biscay. The change in plans was news to everyone but the aircrews. An advance echelon of ground and maintenance staff departed from Langley on C-54 transports at the end of November and made it as far as Accra, on the west coast of Africa, where they sat for a month waiting for transport the rest of the way. No one had apparently decided where exactly in England the squadrons were to be based or who they reported to, so several of the Liberators that followed on the southern route via Africa arrived at airfields there with no idea where to go next. They were “passed from station to station in Africa because no one knew where to order them,” reported their commanding officer. In mid-January Lieutenant Colonel Jack Roberts was still trying to find four of his planes; he reported to Army Air Forces Antisubmarine Command back at Langley that “they were known to be somewhere in Africa.”

Roberts was able to get somebody to decide that they would be based with Coastal Command 502 Squadron at St. Eval in Cornwall, but though the RAF greeted them warmly, no preparations had been made and conditions were frankly abysmal. The field’s facilities were already overstretched and there were no hangars available at all for the American planes. Maintenance had to be done in the open air during the limited daylight hours. None of Roberts’s men had been issued winter clothing: another administrative slipup apparently due to word not having caught up with their change in orders from North Africa. Roberts spent two days trying to get through by phone to the only American air force authorities he could find in the country, VIII Bomber Command headquarters outside of London. He finally was able to get its commander, Brigadier General Ira Eaker, to issue an order placing his unit under Eaker’s command for administration and supply and under RAF Coastal Command for operational control.
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Worst of all was the food. The Americans were literally incredulous at how bad the meals were in the RAF mess. “Unbelievably bad,” recalled one
American officer. “The mess seemed to be a continuous diet of cabbage. Brussels sprouts were considered a rare treat and once we were given cauliflower with a cream sauce for dessert!” That apparently was the norm in the wartime service; an RAF officer at another base in England recalled endless breakfasts of pig’s liver and the mess hall’s “combined tea and cocoa urn” that produced tea-flavored cocoa at breakfast and cocoa-flavored tea at supper. Roberts’s men were eagerly awaiting the establishment of their own mess, which they had been promised would begin operating in February, and the chance to have “some real American chow.”
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Phil Morse and Bill Shockley made their own arduous transatlantic crossing a week after the first of Roberts’s B-24s. It would be the American operational researchers’ first chance to confer with their British colleagues, a step Morse felt was long overdue. He was well aware how isolated the American scientists in general were, and how much they still had to learn from their more experienced British counterparts, who had been fighting a war in earnest for a good two and a half years longer than any of them. “Civilian technical experts here in America tend to stick to their own laboratories and depend on chance contacts from England,” he noted upon his return from England early in the new year. “This is a most dangerous practice, which may lead to serious consequences. It is necessary for our technical men to get across as often as possible to see what is going on.”
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