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machine’s unparalleled cryptographic security, Wilde thought, led many students to think its physical security not so terribly important. Wilde, the bestin his class, was assigned to U-boats; after specialized submarine training, including instruction in acoustic detection, he was assigned to the U-110.
    There, in the closetlike radio room, he stood four-hour watches, chatting or reading a book and playing phonograph records over the loudspeaker system for the crew while listening for a signal through the whistlings, peepings, and static that filled his earphones. As soon as he heard the tone of the transmitter, he would turn down the phonograph, stop talking or reading, and begin taking down the Morse message. All messages were taken down, even those addressed to other U-boats; all were deciphered and given to the captain. The locations of other submarines and of convoys were entered on charts. Wilde never received more than four messages on a watch; sometimes none came in. To minimize the number of transmissions and to eliminate clues to its location, a U-boat did not signal receipt of a message. Garbled transmissions, which are difficult or impossible to decipher, were relatively rare; to ensure that important messages were not missed, U-boat headquarters repeated each one half an hour to an hour after the first transmission. During an action, the radioman worked the listening apparatus. This array of hydrophones gave the range and bearing of sound sources, such as torpedo explosions and attacking enemy warships; Wilde thought the data it yielded were imprecise.
    On April 21, the day after the U-110 reached the waters west of Ireland where she would begin her patrol, Dönitz radioed her an attack location, AL58 on the
Kriegsmarine
grid, 400 miles west of Ireland’s west coast. The next day, Dönitz ordered “Attack!” Three days later, Lemp sank a 2,500-ton ship steaming alone. He missed on April 28 with a single shot on a fishing trawler. Dönitz moved the U-110 south, then north, then west over the eastern Atlantic, perhaps on the basis of German codebreaking that told him where convoys might be.
    On Thursday, May 8, Lemp saw smoke and the mast of a warship. Coming up on her starboard, he discovered that she was escorting a slow-moving convoy heading west at 7 or 8 knots. He transmitted a sighting report, which was intercepted by the British Admiralty. It determined the location of the transmitter by a direction-finding fix, then compared the location with its plot of convoys at sea. At 7:07 P.M ., Greenwich mean time, the Admiralty warned OB 318 that it was being shadowed. The convoy altered course 30° to port, away from the U-110.
    At about the same time, Dönitz ordered other U-boats to report their positions and directed Lemp to maintain contact with OB 318 and to attack if possible. But the convoy’s turn away broke Lemp’s contact until the listening apparatus again detected the convoy. However, Lemp was unable to take action because the moon was too bright. He decided to attack the next day, when two other U-boats were expected to be nearby. At 2:16 A.M . local time on Friday, May 9, he again reported the convoy’s position; Dönitz ordered several U-boats to concentrate. A few hours later, the U-201, commanded by Lieutenant Adalbert Schnee, hove into sight. Using light blinkers to communicate, the two captains agreed to attack that day, Lemp first.
    Early that morning, Baker-Cresswell came onto the bridge of the
Bulldog
to watch his group take up its day screening positions. It was to be his last day with the convoy. His ship would leave late in the afternoon with sufficient fuel to return to Iceland. By that time the convoy could disperse; it would then be at about 34° west longitude, and no Axis submarine had ever sunk a ship that far west. His good feelings were reinforced by the arrival of his breakfast, wrapped in a napkin and served by his faithful steward. As the morning wore on and nothing