Seizing the Enigma: The Race to Break the German U-Boat Codes, 1933-1945

by Kahn, David

  A. Dillwyn Knox, who made some progress in the attempt to solve the Enigma.

  Marian Rejewski, the Polish mathematician who solved the Enigma.

  The U-33 and some of her crew members.

  The Führer greets von Dresky, skipper of the U-33.

  Fish-oil tanks burn during the British commando raid on the Lofotens, March 1941.

  The Krebs just before the British boarded her during the Lofotens raid and seized Enigma keys and rotors.

  The ice-encrusted gun and the crew of the ill-fated U-110.

  Sub-Lieutenant David Balme of the Bulldog, who boarded the U-110.

  Radioman and Enigma machine operator Heinz Wilde of the U-110.

  Four key members of the British codebreaking agency: Edward Travis, its head from 1942 on.

  Harry Hinsley, who evaluated solved German intercepts.

  Hugh Alexander, head of the cryptanalysts of German navy messages.

  Gordon Welchman, whose device accelerated cryptanalysis.

  Codebreakers play rounders on the lawn of Bletchley Park. In the background is the main house.

  Codebreakers watch a rounders match at Bletchley Park. Fifth from left, standing, is George McVittie, head of meteorological cryptanalysis. Standing at right is A. G. Denniston, then head of B.P.

  The boarding party of the Tartar musters on her forecastle as the British destroyer approaches the German weather ship Lauenberg.

  The boarding party seizes all the papers it can find, including cryptographic keys, from the Lauenburg.

  The crew of the weather ship, blindfolded, is taken aboard the Tartar.

  The Tartar sinks the Lauenburg with gunfire.

  The conning tower of the U-559 emerges from the sea, its white donkey emblem picked out by the searchlight of the destroyer Petard.

  Antony Fasson, who lost his life getting cipher documents from the U-559.

  Admiral Karl Dönitz, commander of U-boats.

  The giant wall plot of the North Atlantic, which showed the positions of convoys, escorts, and U-boats, in the headquarters of Western Approaches command in Liverpool. The circles showed areas to be avoided by Allied U-boat hunters because of the presence of Allied submarines.

  A high-speed U.S. Navy mechanism, called a bombe, that tested for possible Enigma solutions.

  Commander Kenneth A. Knowles, head of the U.S. Navy’s Submarine Tracking Room, which depended heavily on Enigma solutions.

  Some of the U.S. Navy personnel of OP-20-GI-2(A) who solved, translated, and evaluated Enigma intercepts. Among them are Erminnie Bartelmez, at extreme left; Marjorie Boynton, with blond hair, looking to her right; Knight McMahan, with hat at his feet; Bernard Roeder, commander of the unit, holding his hat; and Willard Van Orman Quine, standing behind seated William Lindsay.

  A depth charge, dropped by a U.S. Navy torpedo-bomber during a U-boat refueling rendezvous, drenches the tanker U-117, whose bow emerges from the spray just before the U-66 dives.

  An F4F-4 Wildcat from the aircraft carrier Card attacks the U-117, which circles in an effort to escape.

  The U-117 races desperately through the sunlit sea as a depth charge explodes near her. Minutes later she was sunk.

  13

  THE STAFF SCHOOL MEMORY

  TWO DAYS AFTER THE MÜNCHEN WAS CAPTURED, AND ON THE other side of Iceland, Fritz-Julius Lemp’s U-110 was forced to the surface by the attacks of Joe Baker-Cresswell’s Escort Group 3. As the submarine broke water. Baker-Cresswell ordered the heavy guns of his ship, the Bulldog, to open up on the U-boat. Then, intending to ram, he swung the Bulldog to port and called for 12 knots.

  In the submarine, Lemp ordered the crew to put on diving vests and abandon ship. Discipline held. There was no panic, no jostling to be the first out. The young radioman, Heinz Wilde, forgot temporarily that his diving vest was in the radio room, then remembered, got it, and put it on. His brain was half on automatic after the overwhelming terror he had felt under the depth-bomb attack of moments before, when he thought his boat would go down and his life would end. So he got his cap and put it on but left his camera behind. Lemp opened the conning tower hatch, and someone else opened the forward hatch. The first men emerged from the conning tower.

  Baker-Cresswell, recalling the story of the codebook recovered from the Magdeburg, ordered his ship full speed astern and his guns to cease firing.

  The former order worked better than the latter. Within a couple hundred yards, the Bulldog had halted. It was harder to get the gunners to stop firing. The heavy weapons—the 4.7-inch, the 3-inch, the pom-poms—indeed ceased. But from behind Baker-Cresswell “a dreadful noise” shattered his ears: one of his officers was firing the Lewis submachine gun, something the officer had always wanted to do. As the Germans poured out of the conning tower and the forward hatch, the British sailors, perhaps fearing that the enemy was about to man the cannon on the forward deck, continued to fire their small arms; guns on the other British warships, by now in a circle around the U-boat, also shot at her. Some of the Germans were killed. Those who seemed about to serve the cannon scattered and dove into the water. The dots of heads littered the ocean. Some moved; some had arms that flailed in the water; some were motionless. Then one of the other destroyers, the four-stacker Broadway, raced toward the submarine, apparently trying to ram her and thereby unwittingly end Baker-Cresswell’s plan to salvage the codebooks. He grabbed a megaphone. “Keep clear!” he shouted at her. But would she hear? He ordered a signalman to flash the message to the Broadway, But would she see it? Could she stop in time?

  The crew members still inside the U-boat heard the shooting and sensed or were told that the first men to emerge had been shot. This decreased whatever urgency there may have been to get out. Silence fell over the crew. Wilde wondered whether he should even climb out. Suddenly, as the Broadway raced toward the U-110, Lemp shouted, “Out! Out! The destroyer is going to ram us.”

  Wilde knew that if capture threatened, the boat’s secret documents, including the cipher material, were to be destroyed. But the submarine’s rise to the surface had been so swift and unanticipated, especially in face of the expectation moments earlier that the vessel would go down, that no preparations had been made to wreck the Enigma and soak its keys, printed in water-soluble ink. None of his three superiors in the boat’s radio service had taken any steps to throw the machine or its papers overboard or otherwise render it useless to an enemy. And he had been indoctrinated with the belief that the machine was cryptographically so secure that even capture would not compromise its secrets. Still under the impress of the terror of death, he was not able to react calmly. And now, with the captain’s shout raising in him the new fear that thousands of tons of steel were about to smash into his frail vessel and do what the depth bombs had failed to do, all thoughts of cipher machines vanished from his brain.

  Wilde climbed up the ladder in the conning tower, went out onto the bridge, heard Lemp order, “Overboard!” and jumped 15 feet into the Atlantic. As he went down, he never thought about whether the water was cold or even that it was wet, only that it was a beautiful turquoise color. Still descending, he turned on the oxygen flask of his diving vest. It brought him up. His cap was floating next to him and, still in a trancelike state, he reached over and put it on. He saw others swimming in a group. The cook, next to him, said, “I’m swimming to a destroyer.” Then the group of men, to keep their spirits up, began to sing one of the songs Wilde had played over and over on the submarine’s loudspeaker system: “Im Leben Geht Alles Vorüber” (In life all things come to an end).

  The Broadway, meanwhile, continued speeding toward the submarine. She did not intend to ram. Her plan was to drop two depth charges under the U-boat set to explode at about 100 feet to damage the sub so that she could not dive again and to encourage her crew to abandon ship. But the firing of the Broadway’s 4-inch guns had cracked her bridge windows so extensively that they were almost opaque, and her captain did not realize that he was on a collision course. He drop
ped his depth charges and at the last moment turned away, but the stern of the submarine, whose port motor had been running slowly, swung toward the destroyer. As the Broadway passed by, the U-boat’s after hydroplane sliced open the destroyer’s port forward fuel tank. Oil spilled into the water.

  By then Baker-Cresswell had enforced his cease-fire order and, with his ship drifting only a hundred yards from the U-boat, was ready to realize his idea of boarding her. No plans had ever been made for the possibility of boarding a U-boat, so no training or drill had ever been carried out for it.

  “Organize boarding party instantly,” Baker-Cresswell said to his second in command, Lieutenant John Aitken. “The sub-lieutenant will be in charge.”

  The sub-lieutenant was David E. Balme, who in joining the navy had followed a long family tradition. Balme, just twenty, with a mischievous look and a twinkle in his eye, was once characterized as a type who made girls happy when he came ashore. He had studied at the Dartmouth naval school and sailed on training cruises in the Mediterranean and was serving aboard a destroyer as a midshipman when the war began. He liked the life and the responsibility, and in February 1941 he joined the Bulldog.

  Someone hailed him: “Hey, you, sub! Away you go!” He reported to the bridge.

  Baker-Cresswell instructed him. “Your job is to secure all important papers, ciphers, charts—anything that you can find.” Balme armed himself with a huge service revolver—as dangerous to him as to the enemy, he thought—and the eight ratings (enlisted men) with rifles, revolvers, hand grenades, and gas masks (in case sea water had evolved poisonous chlorine gas from the batteries). The ship lowered the 27-foot, five-oared whaler off its port side into the water. It was 12:45 P.M., Friday, May 9, 1941.

  The Bulldog was lying to the windward of the U-boat, and a heavy swell was running. It would have been safer to row around the submarine and come up on her leeward side, but this would have taken more time, so Balme made directly for her. Suddenly Baker-Cresswell saw two men who appeared to be manning her forward gun. He gave the order to open fire with the Lewis gun, and the two men appeared to be hit. Within moments, the U-110’s whole crew seemed to have jumped or fallen into the water. They were picked up by the Broadway and the corvette Aubretia and promptly hustled below, so they were unable to see anything outside.

  As the whaler approached the submarine, no fire came from her, so Balme grew confident that no one was in the conning tower. He could see the numerous holes in the conning tower made by the Bulldog’s 3-inch gun and pom-poms. The bowman in the whaler leaped onto the U-boat with the light line, and Balme and the others followed, clambering onto the slippery hull. Soon one of the ocean swells carried the whaler onto the U-boat, jamming it between the conning tower and the steel guard rails. The pounding of the waves soon broke it up. Balme felt it was almost suicidal for an inexperienced man to climb down the conning tower of a submarine with one hand holding a weapon. So he bolstered his revolver. The sailors balanced themselves on the narrow, rocking deck, carrying their unwieldy weapons and trying not to accidentally shoot themselves or one another.

  Balme climbed part way up the conning tower and entered through an opening on the starboard side. At his feet he saw a closed hatch. The boat had indeed appeared to be deserted, but if the hatch was closed, perhaps someone was aboard after all. For who would carefully close a hatch after abandoning a vessel under attack? And if the submarine was to be scuttled, wouldn’t its captain want the hatch to remain open, to let water in and air out more quickly? Cautiously Balme turned the wheel that held the hatch screwed down, released a clip, and watched the hatch spring open. He saw the lower conning tower, empty, with a similar hatch at the bottom, also closed. The same question arose: Was the submarine really deserted? If not, anyone in the control room just beneath that second hatch would be able to shoot Balme before he could fire back. The sub-lieutenant briefly considered dropping a grenade inside. But that would defeat the purpose of the boarding. He was there to do a job. He went down the ladder and opened the second hatch.

  More than a bit scared, and feeling very vulnerable, he climbed down into the control room. All the lights were on. Everything was silent except for the hiss of air escaping and the rumbles of distant depth charges. Hatches forward and aft were open. A large metal splinter from a conning tower hit lay on the deck. The control room was deserted—but were crew members lurking nearby, ready to kill their enemies? Would scuttling charges soon go off? Would the depth charges detonate them? Was sea water pouring in somewhere?

  None of these things seemed to be happening, and no German appeared. Balme called the rest of the boarding party down into the submarine. As it became evident that no one was on the boat and no chlorine had been produced, they put down their weapons and their gas masks and looked around a little more carefully.

  The submarine had clearly been abandoned in great haste. A plate of shrimps lay in the radio room. Books and gear were strewn about. The first quick examination took about five minutes. Balme ordered his party to send up all useful documents and equipment. He had signalman William Pollock wigwag a message that the boat was abandoned and appeared seaworthy and towable and that he was collecting gear. He ordered all books sent up except obviously recreational ones, so he recovered some general navigational texts in addition to the log books, signal books, and charts with heavy black lines showing the swept channels through minefields. The men passed these out of the ship by means of a human chain.

  Baker-Cresswell watched nervously from the Bulldog, fearful that the men might drop into the sea the documents for which he had risked violating the Admiralty’s basic instructions to escort commanders: “The safe and timely arrival of the convoy is the primary object, and nothing relieves the escort commander of his responsibility in this respect.” In one anxious moment, he saw Able Seaman Claude Wileman stagger from the conning tower protecting an armful of documents with his body. He moved in spurts, hurrying a few paces, then holding on to the guard rail as a sea rocked the boat, then moving on. Once a wave all but covered him. He emerged, soaked but safe, and with the documents. Nor did any of the other seamen who maneuvered so carefully on the U-boat’s narrow hull lose anything. They put their treasures into a motorized whaler from the Broadway that had replaced the Bulldog’s smashed boat.

  Meanwhile the telegraphist in the party, Allen O. Long, went to the radio room. It had apparently served as the boat’s office, for he found pay books and general correspondence as well as signal logs. He saw also the two compact high-frequency transmitters and the two receivers, a Telefunken and a civilian broadcasting receiver; he noted their settings. He also considered that the sets seemed far less complicated, far more compact than the Royal Navy’s. And there Long saw as well a device that looked like a typewriter. It was still plugged in, drawing its current from the boat’s power supply and not its own batteries, and appeared to have been in use when the U-boat was abandoned. Long pressed the keys. But the results seemed “peculiar”—pressing an a did not light up an A on the illuminated panel. It was not, therefore, just a special form of typewriter. Balme examined it as well. He hadn’t thought of cipher machines before, but he recognized it for what it was and understood that it was useful. It was bolted to the table. Long unscrewed the bolts by hand and passed the machine out of the submarine via the human chain to the Broadway’s whaler, which took it, and the documents, to the Bulldog.

  Two boatloads of equipment went over, and Baker-Cresswell was pleased to see that the German papers printed in water-soluble ink had lost only small portions of their text. Balme also passed up half a dozen sextants, which he regarded as of superb quality, far superior to those supplied by the Admiralty, and nine of ten Super Zeiss binoculars. The tenth was not handed in, Balme later finding it by far the best binoculars he had ever used.

  The minutes turned into hours as Balme continued to scour the ship. Among the officers’ belongings he found some wallets, slips of paper, cameras, a movie camera. In the radio room there
was writing paper with well-printed letterheads and envelopes, ordinary books, cards, dice, and what he called “the usual art studies.”

  He was impressed by the U-boat. She was “new and a fine ship both in the strength of the hull, in the fittings and instruments and general interior construction. … Spotlessly clean throughout. Ward Room finished off in light varnished woodwork and all cupboards were numbered with corresponding keys to fit.… Plenty of tinned ham, corned beef and three sacks of potatoes in control room; also luxuries such as beer, cigars, Players cigarettes (German printing on packets).… Magnificent galley.…”

  The Aubrietia and the Broadway picked up survivors while the Bulldog’s engineer officer went over to see whether the U-boat was seaworthy and to stop the port motor from its slow turning. He concluded that the vessel was able to stay afloat, and he slowed the motor by shifting what he presumed to be the central rheostat to the off position, but the shaft did not stop revolving. Nor did various other adjustments of the rheostat succeed in stopping it. And after a time the boat seemed to be a little more down by the stern than when he had come aboard.