Seizing the Enigma: The Race to Break the German U-Boat Codes, 1933-1945
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For almost four desperate years, from 1939 to mid-1943, the British and American navies fought a savage, losing battle against German submarine wolfpacks. The Allies might never have turned the tide without an intelligence coup. The race to break the German U-boat codes is one of the greatest untold stories of World War II. Kahn expertly brings this tale to life in this newly-updated edition of his classic book.
Soon after war broke out, Hitler’s U-boats began to sever Allied lifelines. In the gray wasteland of the North Atlantic, submarines prowled; at night, the sky lit up with the flames of exploding tankers. To meet the growing crisis, ingenious amateurs joined the nucleus of dedicated professionals at Bletchley Park. As the Battle of the Atlantic raged, they raced to unlock the continually changing German naval codes. Their mission: to read the U-boat messages of Hitler’s cipher device, the Enigma.
Critical to their success was a series of raids at sea. U-110, captured intact in the mid-Atlantic, yielded the Enigma machine itself and also a trove of secret documents. The weather ship Lauenburg seized near the Arctic ice pack provided codesettings for an entire month. In the Mediterranean, two sailors rescued a German weather cipher than enabled the team at Bletchley to solve the Enigma after a year-long blackout.
crib may not have worked, for, as was later learned, a different U-boat had sunk both ships. But when one crib failed, the cryptanalysts tried different suppositions. The codebreakers worked in close collaboration with Hut 8. The British forwarded messages that could not be intercepted in the United States, and the teams on both sides of the Atlantic sought cribs, dividing up the work by days. When the British found a crib, they transmitted the text of the intercept followed by the text of the
U-Boat Command was mulling this over, SC 127 marched at about 7 knots along its predetermined course, passing Points C, D, and E as it headed first southeast out of Halifax and then east. Upon reaching E, at 6 P.M. Sunday, the eighteenth, it turned onto a course of 66°, or east-northeast. The barometer was now falling and the sky had clouded over, but the sea remained smooth and the air calm. Allied cryptanalysts had solved that day U-Boat Command’s long two-part message of the seventeenth
climbing turn, he saw a shock wave centered about 25 feet from the submarine’s starboard side and just forward of her conning tower. It swept to her port side and appeared to lift her from below and make her list to port. Then a heavy column of water about 100 feet high obscured the U-boat. When she reappeared, she was turning to starboard. Paulson attacked again. He saw half a dozen figures, some inert, on the conning tower. His shots killed one sailor who had kept firing despite several wounds,
cryptanalysts, under Turing. Here he became a remarkable asset. His intellect was powerful—one of his coworkers later said that “Alexander was one of the most intelligent people I’ve known, and I’ve known a lot of intelligent people”—and his vitality extraordinary. A lively, talkative, enthusiastic person, he incorporated several contradictions. Though he worked in the solitary pursuit of mathematics, he dealt with people extremely well. He proved an excellent organizer and administrator though
declining. In January 1941 Thring was replaced by his assistant. The move was revolutionary: the assistant was not a career officer but a thirty-seven-year-old barrister appointed a temporary commander in the Royal Naval Volunteer Reserve; for the hidebound navy to appoint a civilian to such a critical department was unprecedented. But those who sought the change knew their man. Rodger Winn had worked under Thring since August 1939. He was of medium height, broad, with powerful shoulders but a