Alan Turing was one of the most influential thinkers of the 20th century. In 1935, aged 22, he developed the mathematical theory upon which all subsequent stored-program digital computers are modeled.At the outbreak of hostilities with Germany in September 1939, he joined the Government Codebreaking team at Bletchley Park, Buckinghamshire and played a crucial role in deciphering Engima, the code used by the German armed forces to protect their radio communications. Turing's work on the version of Enigma used by the German navy was vital to the battle for supremacy in the North Atlantic. He also contributed to the attack on the cyphers known as "Fish," which were used by the German High Command for the encryption of signals during the latter part of the war. His contribution helped to shorten the war in Europe by an estimated two years.