Blackett's War (29 page)

The U-boat men increasingly relieve the strain in total dissipation ashore. At a bacchanalia the night before their departure, the officers of the boat Buchheim’s narrator is assigned to are soon far beyond inebriation, staggering back and forth between a nightclub and the nearby whorehouses of the French port town. One officer passes out in the lavatory in a pool of urine and vomit; another solemnly pours beer into the piano; another pulls out his service revolver and sends the rest of the drinkers diving under their tables as he shoots out, one by one, the classical mythological figures tastefully depicted on a mural over the orchestra platform. Gestapo officers morosely but silently watch the proceedings.

If the corvettes were little more than floating depth charge platforms, the Type VII U-boats were little more than seagoing torpedo platforms. Each boat carried twelve torpedoes, each twenty-three feet long and weighing two tons. The torpedoes were the boats’ raison d’être and imperative and everything gave way to their needs—comfort, space, payload, work schedules. The foremost compartment of the boat was where most of the regular seamen bunked but its name was the torpedo room, which accurately reflected priorities. Four torpedoes were kept loaded in their firing tubes; six reloads had to be accommodated on and beneath the deckplates, taking up space in the already impossibly cramped room, barely ten feet wide and not tall enough for a man to stand up in. In what space was left over twelve bunks hung in rows, shared by twenty-four men who took turns sleeping in them in shifts—“hot bunking.” The torpedoes, almost like living things, demanded constant nursing and tending. Every few days their delicate mechanisms had to be checked and adjusted, batteries charged, guidance and depth-setting systems inspected. When that happened, the bunks had to be stowed away, the deckplates pulled up, the torpedoes in their tubes manhandled partway out and the whole room became more machine shop than living space.

The officers and petty officers occupied only slightly more roomy
compartments farther aft. Every compartment doubled as passageway, mess room, and workspace; sleep was constantly being interrupted by the mechanics and seamen passing to and from the engine room, control room, or bridge for their watches, by tables being folded out for mealtimes (when the lower bunks served as benches), by deckplates being wrested up to get at batteries or other equipment. The control room at the center of the boat was an incredible maze of cable chases, compressed air pipes, gauges, and dials that gave one the feeling of crawling through the innermost workings of a power plant or factory. There were two toilets for the forty-four officers and men, but the one next to the galley was inevitably given over to the more pressing needs of storage and was usually crammed with crates of vegetables, potatoes, cheese, cans of coffee, bottles of fruit juice. (“More space for food and less for shitting! You try to make sense out of it!” the bosun boisterously declares to Buchheim’s narrator.) At the start of a cruise, moving anywhere meant ducking or dodging around hanging provisions: sausages and sides of bacon suspended from the ceiling of the control room, loaves of bread filling hammocks in front of the radio room.

Whenever the boat was running on the surface four men stood watch on the bridge, each assigned one quadrant to scan constantly; in even a small chop waves crashed over the deck drenching the lookouts. Still, the fresh air was a welcome relief for most; below the stench was a constant presence; it hit you like a physical force, a mixture of diesel fumes, lubricating oil, engine exhaust, damp rot, cooking odors, and the acrid and omnipresent fug of unwashed bodies, ineffectually masked with cologne. After a few weeks green mold grew on leather belts, black mildew on shirts, thick crusts of yellow fuzz covered the bread, and faces and arms were pocked with infected scabs and boils.
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The discomforts of day-to-day life were nothing compared to Buchheim’s descriptions of experiencing a depth charge attack: hours on end of cat and mouse, lying still hundreds of feet down, the churning propellers of destroyers and corvettes growing steadily louder, followed by the relentless rain of blasts, each of which could split the pressure hull open like a can opener, with certain death to follow.

FOR THE THREE MONTHS
preceding Churchill’s Battle of the Atlantic Directive, British escorts had not sunk a single U-boat. That changed on March 7, 1941—the very day following the prime minister’s order to “take
the offensive.” The corvette
Camellia
, escorting a westbound convoy south of Iceland, sighted a U-boat on the surface. A second corvette, HMS
Arbutus
, joined the attack, and over the next four hours the ships repeatedly depth-charged a spot where air bubbles were seen rising to the surface. Survivors from the U-boat—she would turn out to be
U-70
, under the command of Kapitänleutnant Joachim Matz—later told their British captors that the explosions had started a leak that sent the boat sinking out of control. The depth gauge hit 200 meters—its maximum reading—and still the boat kept dropping farther as cracking sounds rent the hull and paint began flaking off the sides of the walls. With only a small quantity of compressed air in reserve and the stern down at an angle of 45 degrees, the crew huddled in the forward compartment to try to bring her on an even keel, set the electric motors full ahead, and blew the tanks. As the boat broke the surface the crew opened the scuttling vents and spilled out of the conning tower. The British ships fished Matz and twenty-five of his officers and men out of the water; twenty others were lost.
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Over the next week and a half three more U-boats were sunk by escorts in depth charge and ramming attacks. Otto Kretschmer of
U-99
, Dönitz’s top ace, was taken prisoner; Joachim Schepke of
U-100
, the next highest in the tonnage score, was crushed to death when the destroyer
Vanoc
sliced through her conning tower, ramming the surfaced boat as she tried to flee in the darkness; Günther Prien and
U-47
were lost either in a depth charge attack or from some other cause. The string of British successes had to be partly coincidence, but they were a harbinger that the tide of the battle was shifting at last.

Just after noon on May 7, 1941, a Royal Navy task force of three cruisers and four destroyers reached a bleak stretch of ocean northeast of Iceland, changed course to the east, and formed into seven parallel lines spaced at ten-mile intervals. For the rest of the day they steamed steadily eastward, combing a square of sea sixty-nine miles on a side, which was one degree of latitude. Harry Hinsley, the young German history student who had become Bletchley Park’s authority on German naval communications, had determined that somewhere within that patch of ocean, designated on German charts as grid square AE 39, was the German weather trawler
München
. Aboard her, Hinsley fervently hoped, were the maddeningly elusive pieces of the puzzle that would allow the Bletchley code breakers to crack the naval Enigma once and for all.

In the fading afternoon light a lookout aboard the cruiser
Edinburgh
spotted smoke on the starboard bow. After a short chase two of the destroyers
overhauled the German trawler and sent a few shells hurtling into the water near her; the crew promptly abandoned ship and a boarding party from the destroyer
Somali
, which had meanwhile raced alongside at top speed, leapt aboard. They were soon joined by an officer from the
Edinburgh:
Jasper Haines, a captain in the Naval Intelligence Division. He seemed to know exactly what he was looking for, the other members of the boarding party later recalled, making his way directly belowships and returning a few minutes later with a bundle of papers in his hand. Within a few hours Haines was heading for Scapa aboard the destroyer
Nestor
, with orders to get to Bletchley as soon as possible with his finds.
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Two days later an unplanned bonus was added to Hinsley’s haul. The destroyer
Bulldog
was escorting a westbound convoy of forty ships when two enormous torpedo blasts suddenly erupted in the bright noon. The
Bulldog
’s captain, Commander A. J. Baker-Cresswell, sheered off from the head of the column with two corvettes to chase down the attacker. Almost at once the corvette
Aubretia
made asdic contact and began dropping depth charges. Only moments after having turned and dropped a second pattern of depth charges, the escorts were rewarded with “the dream of all escort vessels,” as Sublieutenant David Balme of the
Bulldog
put it, the sight of a U-boat blown to the surface. Thinking quickly, Baker-Cresswell saw the chance to capture the boat before her crew could scuttle her, which was the standard German practice. He ordered his crew to open fire with every available weapon. A hail of shells and bullets from the ship’s two 4.7-inch guns, machine guns, even an antiaircraft gun clattered in deafening syncopation against the metal hull of the U-boat. The German crew began spilling out onto the deck and into the water.

Baker-Cresswell turned to Balme. “Right, we will board her. Sub, you take this sea boat.” Balme was twenty years old, the sea boat was a rowboat propelled by five oarsmen, and the sea was running with six-foot rollers. Reaching the U-boat, Balme climbed into the conning tower, waved his revolver around a bit wondering apprehensively if any Germans were still down there, and plunged down the ladder. The boat was deserted. Balme formed the rest of the boarding party into a human chain and passed charts, books, papers, and gear up the ladder and into the sea boat. The captured boat,
U-110
, was taken under tow by
Bulldog
but sank the next morning (“one of the greatest blessings in disguise,” Balme later understood, as it kept the Germans from learning that the British had been able to retrieve the critical documents from the boat).
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On May 13 a Royal Navy intelligence officer met the returning ship at Scapa Flow, and that same day he was on a plane for London, and then on to Bletchley Park, where he arrived that afternoon. That night at 9:37 the teleprinters at the Admiralty’s bombproof concrete “Citadel” in Whitehall came rattling to life with the start of an uninterrupted stream of a hundred deciphered naval Enigma messages from the Bletchley code breakers.
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THE BREAKTHROUGH HAD COME
from a list of daily settings for the naval Enigma network taken from the
München
and, even more priceless, the external code tables used to encrypt the eight-letter indicators which specified at the start of each message the precise starting position of the rotors used for the machine for that particular message. Those tables were among the haul of papers from
U-110
. (Balme had also retrieved an intact Enigma machine, but that added nothing the code breakers had not already long had in hand.)

Since the previous summer the Bletchley cryptanalysts had been breaking army and air force Enigma traffic using the first of the behemothlike mechanical calculators they called the “bombes.” Built by the British Tabulating Machine Company, they cost £5,000 apiece, weighed one ton, emitted a perpetual stream of leaking machine oil, and were plagued with temperamental wire contacts on the dozens of spinning rotors which reproduced the Enigma machine’s wiring. Each little wire brush contact had to be preened with tweezers before each run of the machine to keep them from shorting.
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They were a stroke of mathematical if not exactly mechanical genius. Alan Turing had worked it out in a flash of jaw-dropping insight. The bombes operated on the principle he had discovered, that if one knew or could reliably guess at the plain text that corresponded to several letters of an intercepted Enigma message, a unique pattern was formed in the way those enciphered and unenciphered letters were interrelated from one position to the next in the message; moreover, those patterns had distinct mathematical properties which were unique—or at least nearly unique—for every different setting of the Enigma, and these could be tested systematically to find the setting that had generated them. The bombes used an electric motor to drive the rotors of a battery of interconnected Enigmas through every possible position until the looked-for pattern was electrically detected. Each “hit” could then be tested by setting up an Enigma replica with the setting recovered by the bombe and seeing if it worked to
decode the rest of the message into something that looked like intelligible German.

The problem with the naval Enigma was twofold. First was getting enough reliable “cribs,” those bits of known contents of a message. It was a chicken-and-egg dilemma. Military wireless traffic usually contained an abundance of stereotyped phrases, such as times and dates of transmission, “from” and “to” lines, common abbreviations such as BdU. The process of matching a crib to its corresponding piece of cipher text was facilitated by a peculiarity of the Enigma machine, that a letter was never enciphered by itself: an A in the plain text never became an A in the enciphered message. So a possible crib could be slid along the coded message until a place was found where there were no “crashes,” spots where the same letter appeared at the same position in both plain and cipher text. But without being able to read a few messages to begin with, it was hard to guess what a good crib might be. Moreover, as would later become apparent, the German navy ran a very tight ship when it came to cipher security; wireless operators were instructed to vary common abbreviations and standard phrases, so that BdU for example might be written BDUUU or BEF.UNTERSEEBOOTE or BEFHBR.UUUBTE, or some other variation each time it was used. Finding a way into the system depended on getting a few successes to provide an initial foothold.
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