From Sixteenth-Century Cryptography to the New Millennium — The Last 500 Years - Codes: The Guide to Secrecy from Ancient to Modern Times - page 92

Turing (1912-1954).
Turing was born on June 23, 1912 in London. He studied under Alonzo
Church (1903-1995) at Princeton and obtained his doctorate in 1938. During
World War II, he was employed in the British Foreign OQce, where he got
involved in cryptanalyzing the Enigma cryptosystem. Toward this end, he con-
ceived of a machine called the BOMBE , the first prototype of which arrived at
Bletchley on March 14, 1940. However, it was not as successful as they had
hoped and to compound the problem, the Germans had changed the method of
how they managed keys, deleting repetitions, so decryptions dropped dramat-
ically. They needed a new improved BOMBE, which was not delivered until
later that year, on August 8. In less than two years there were eighteen work-
ing versions of the BOMBE at Bletchley Park. By September of 1941, Field
Marshal Rommel's Enigma cryptograms to Berlin were being cryptanalyzed. In
fact, William Friedman visited Bletchley Park in 1941, exchanging information
on techniques for attacking Purple for British information on breaking Enigma.
By 1942, they had dug deeply into cryptanalyzing Enigma, which played a major
role in the Allied victory.
Figure 2.18: Midway exhibit.
(Courtesy of the National Security Agency Public Photo Gallery.
See http://www.nsa.gov/gallery/photo/photo00010.jpg .)