ide a disabled U-boat, but for some reason the charges failed to detonate in this case. The captain of the boat also failed to destroy his Enigma machine, a coding device that would be decoded before the end of the war and enable the Allies to decipher German transmissions. The fact that the U-100 was captured rather than sunk was kept a secret until the end of the war, for if the Germans knew it had been captured they might change their codes or coding device. Within a week after receiving the Enigma machine, British intelligence analysts had deciphered the code and could read German transmissions:
The U-boat war entered a new phase. The life cycle of a U-boat became an open book. Everything--a U-boat's whereabouts, targets, often even the amount of fuel that it had in its tanks and the number of torpedoes it had available for firing--was revealed.
The U-boat contributed to its own destruction when the Enigma machine fell into Allied hands. The Normandy invasion would be served by the use of the same technology for decoding German communications. The possession of the Enigma machine would provide an opportunity to the Allies, but the Enigma code had to be broken as well to make the machine useful.
Radio messages from the Germans were decoded at Bletchley Park, and because of the ability of the Allies to accomplish this task, this was the first war in which one side was regularly aware of the thoughts and plans of the other side. Another astonishing thing about Ultra was the fact that during the war, its existence was known by several thousand people among British and American forces yet remained a secret from beginning to end:
Ultra undoubtedly brought new dimensions into strategic planning and battlefield generalship, and it has been somewhat loosely said that the Allies might not have won the war without it.
Bletchley Park is a house some 50 miles northwest of London, and it was purchased by the British...