Seizing the Enigma (42 page)

That vessel was in desperate shape. Its deck was awash, and waves broke over it continuously. The rigging and wireless aerials had been almost completely shot away. The top of the conning tower was a shambles; at its base was the hole made by the 4-inch shell; in the middle were two or three dozen punctures an inch in diameter, through which water sloshed. Plates on either side were stove in. The searchlight pinned the U-boat in its dazzle. The Germans in the water cried for help. In the darkness beyond, the
Petard
’s sister ships circled, listening for other U-boats.

Fasson and Grazier reached the submarine and climbed down into her control room. The U-boat’s lights were on, and they could see two bodies there. Fasson shouted up that the submarine was holed forward. Then, using a machine gun, he smashed open cabinets in the captain’s cabin and, finding some keys behind a door, opened a drawer. From it he took out some documents, apparently secret ones.

Tommy Brown had gone below to help Fasson and Grazier, water from the 4-incher’s hole pouring onto his back as he went down the ladder. Now he carried these precious papers up the conning tower and gave them to the men in the whaler. Another sailor, K. Lacroix, at the top of the conning tower, pulled up some books with a line. Brown went down again to bring up more documents, managing to keep them dry despite the leaks and splashes. On his third trip, the water, which had been rising gradually, stood 2 feet deep on the submarine’s inside deck.

Back in the control room, Fasson was trying to free a box containing some instrument—perhaps a radio or radar—from a bulkhead to which it was attached by wires. The water was getting deeper; outside, it was starting to cover the aft gun platform. Brown told the lieutenant that they were shouting on deck for them to come up. Fasson directed Brown to take up the next batch of papers. The teenager climbed the ladder with the documents and passed them into the whaler. Meanwhile, Fasson and Grazier had managed to break away the instrument box and tie it to a line to be lifted up. As the sailors hauled it out, Fasson called out that they were pulling too fast, that the instrument appeared delicate and important and that they should be careful with it.

By now the sea was over the afterdeck platform, and Connell told Brown not to go down again but to tell Fasson and Grazier to get out at once. Brown saw them at the bottom of the conning tower and shouted, “You had better come up!” twice. They had just started up when, unexpectedly and swiftly, the submarine sank. Brown jumped off; Lacroix, still on the conning tower, had to pull against the water
pouring down as he climbed the last two rungs of the ladder. He swam away against the suction, and he and Brown were picked up by the whaler. But Fasson and Grazier had not been able to overcome the inrushing water. They went down with the submarine.

The whaler with its precious documents came alongside the
Petard
and was hoisted on the run as she and the
Dulverton
, their searchlights extinguished, moved at speed away from the possible danger of other U-boats. The euphoria of the crew members at having destroyed a hated enemy quickly turned to an inexpressible sorrow as they realized that they had lost a competent and well-liked officer and a regular serviceman who was an asset to the ship. The
Petard
continued to Haifa, where the valuable documents were given to naval intelligence officers. Thornton, true to his word that he would send a trophy to the ship’s builders, sent a U-boat seaman’s life jacket to Newcastle. After deciding that Fasson and Grazier could not be granted Britain’s highest decoration for valor, the Victoria Cross, because they had not acted in the face of an enemy, the Admiralty posthumously awarded them Britain’s second highest decoration for bravery, the George Cross.

The documents that had cost the lives of Fasson and Grazier included two that were most useful for G.C.&.C.S. in its stalled attack on the U-boat Enigma. One was the current edition of the Short Signal Book. But it was less immediately useful than the second edition of the Short Weather Cipher. That reached Bletchley Park—after the excessive delay of more than three weeks—on November 24. Once again Hut 8 could work the crossruff. It could turn Hut 10’s solutions of broadcast weather messages back into the form the weather messages had when the U-boats enciphered them into Enigma, thus obtaining cribs. But because the second edition of the Short Weather Cipher, unlike the first, did not list the twenty-six rotor settings, each indicated by a letter, to be used in enciphering weather reports, the cryptanalysts thought that all four rotors were used to
encipher weather messages. The tedious testing on the bombes of the possible weather kisses began.

On Sunday, December 13, 1942, Hut 8 struck pay dirt. One of the weather cribs that Archer had brought over yielded a key. It used the fourth rotor in the neutral position, making M4 equivalent to the three-rotor Enigma, the only kind the shore weather stations had. Shaun Wylie, on the night shift, was having breakfast in the canteen when somebody came in and said, “It’s out!” Wylie left his food and went back to Hut 8, where he confirmed the work and telephoned a superior about it. Then he went to Hut 6, Hut 8’s military counterpart. John Monroe was on duty, running the night shift. “It’s come out in the zero position!” Wylie exulted. “Can I have six bombes?” Though Bletchley then had forty-nine bombes, they were in such demand that getting their allocation changed would almost require an act of Parliament, Monroe thought. But recognizing both the importance of the matter and the limitations of his power, he said yes, Wylie could have them—until the day shift came in. In fact, Hut 8 kept them longer.

The cryptanalysts learned that the four-letter indicators for regular U-boat messages were the same as the three-letter indicators for weather messages that same day except for an extra letter. Thus, once a daily key was found for a weather message, the fourth rotor had to be tested only in twenty-six positions to find the full four-letter key. This gave Hut 8 little difficulty. Later that Sunday, solutions of the four-rotor Enigma U-boat key, called
SHARK
by G.C.& C.S., started to emerge.

Late in the afternoon, Hut 8 telephoned the Submarine Tracking Room to report the break into
SHARK
. The call was taken by Winn’s assistant, Reserve Lieutenant Patrick Beesly. The news thrilled him. In an hour the first intercept came off the teleprinter. It revealed the position of fifteen U-boats. Other intercepts arrived in an endless stream until the early hours of the next morning. Beesly began struggling with the difficult and confusing situation revealed by the
intercepts. The night was exhausting but exciting. Gradually over the next weeks the situation clarified. The solutions again permitted evasive routing of the convoys, and sinkings were halved in January and February 1943 from the highs of the two previous months. And, as with the
Magdeburg
, the U-33, the U-110, the
Krebs
, and the weather ships, the precious papers that helped make this success possible had come from an enemy warship.

T
HE GERMAN NAVAL MESSAGES THAT WERE MUCH OF
B.P.’
S RAISON
d’être were intercepted at two main posts: one on the cliffs near Scarborough on the North Sea coast, the other in the center of southern England, near Winchester. Some of the intercept operators, or monitors, were Royal Navy sailors; many others were Wrens.

Among the latter was Alice Axon, a prim and proper teenager who also did direction-finding. As a child in Gravesend, east of London, she had always been keen on signals: she had practiced semaphore as a Brownie and Morse code as a Sea Ranger. At seventeen, the slim young woman volunteered for the Wrens, hoping to be a wireless operator. She stood at the top of her class during the first three months of radio training in London and the second three months in the country. Axon and her fellow students were puzzled because they were taught only to receive Morse, at twenty-five words per minute, and not to send it.

The mystery was resolved when they were sent to the intercept station near Winchester, a large Royal Navy shore installation named as if it were a ship: H.M.S. Flowerdown. The main intercept building had places for about seventy-five monitors, all facing the controllers at one end of a big room. Work went on around the clock. The intercept operators lived in rows of one-story bungalows.

Each monitor listened through earphones to the peepings brought in by the radio set on a high bench in front of him or her. Each
took down all the traffic—every schedule, in the intercept operators’ term—on a single frequency. Axon, for example, copied primarily a frequency used by station DAN at Norddeich, which broadcast weather reports, and secondarily a frequency used by station LLA-bar, whose location she did not know. Some stations transmitted at regular times, others only when they had messages. When nothing was being transmitted, many of the women knitted.

But when a message began, the monitor immediately started to write it down in pencil on the topmost sheet of a pad of intercept forms. No carbon copies were made. He or she noted the time, the frequency, the signal strength, the addressee, and the sender, and wrote down the code groups in the little rectangles on the form’s grid. The monitor was careful to write down only letters of which he or she was certain, omitting the others and indicating the omissions; guesses were not allowed, since a wrong letter was worse than a blank. But the German transmissions were very precise, very uniform; they reminded Axon of the goose step. When a transmission was completed, the monitor ripped the intercept form off the pad and held it up high. Often he or she was holding up one message while taking down another. A controller would take it to the teleprinter to be sent to the codebreakers.

The breaks into
SHARK
, the Atlantic U-boat key, of December 13, 1942, were followed by others. Not all keys could be recovered: in January 1943 no settings were recovered for a ten-day period, and none were found between February 10 and 17. Except for difficulties like these, however,
SHARK
solutions, early in 1943, rarely took longer than seventy-two hours and often less than twenty-four, making them of operational value.

Then disaster loomed. Hints appeared in the traffic that the Germans were going to replace the Short Weather Cipher that had just been recovered from the U-559. The new, unknown edition—the third—would cost Hut 8 its kisses. The first sea lord messaged the vice chief of the naval staff, then in Washington, that “U-boat
Special Intelligence has received a severe setback. After 10th March it is unlikely that we shall obtain more than 2 to 3 pairs of days per month and these will not be current. After 2 to 3 months the situation should improve considerably.”

The first sea lord was too pessimistic. When the new weather cipher went into effect, Hut 8 used the Short Signal Book taken from the U-559 to find cribs among the numerous short signals being emitted by the U-boats during the heavy convoy battles then going on. Like the weather code, this book used the Enigma in three-rotor mode, which speeded up the work of the bombes. Hut 8 fitted cribs to cryptograms by identifying U-boats through direction-finding, radio fingerprinting, and transmitter identification by
TINA
as well as through an index of the behavior and procedures of individual submarines and their skippers. As a consequence, of the 112 days from March 10 to the end of June, Hut 8 solved the
SHARK
keys for 90.

On July 1, however, yet another complication appeared: the Germans brought into service an alternative fourth rotor. Called gamma, it sometimes served in place of the original, called beta (no alpha rotor was ever recovered). Hut 8 reconstructed its wiring crypt-analytically within a few days. The cryptanalysts learned that the choice of rotors was made on the first of the month. This regularity simplified Hut 8’s task: it was only when making the first break of a month that they had the extra task of determining which fourth rotor was being used.

As the convoy battles subsided and the supply of short signals dwindled, Hut 8 exploited the kisses between texts, such as general orders that were transmitted in three-rotor Enigma to surface forces and shore stations and in M4 to U-boats. These provided longer and more reliable cribs, but they took longer to test on the bombes than the short signals.

Bletchley’s first bombe,
AGNES
, was installed on the grounds of the park itself. But to minimize damage from air raids, such as the one
during the night of November 20–21, in which a direct hit destroyed a telephone exchange and a typists’ room and a near miss burst six paces from Hut 4, the next bombes were sited elsewhere. A low, one-story brick utility building was constructed for them at Wavendon Manor, about 3 miles northeast of Bletchley. Still, by the spring of 1941, the codebreakers had only eight bombes and, by the end of 1941, only twelve. Huts 6 and 8 shared the bombes in those days of paucity. The question of who should have them was often difficult but only rarely resulted in fights—usually when Hut 6 was being pressed strongly to break an Afrika Korps key. One reason for this relative harmony was that the deputy heads of the huts at that time—Stuart Milner-Barry for 6 and Hugh Alexander for 8—were good friends. Another was that Milner-Barry always believed, correctly, that losing the Battle of the Atlantic would mean losing the war; he often yielded his bombe time to the naval cryptanalysts, without, however, telling those who were pressing him for breaks.