William Gordon Welchman (15 June 1906–8 October 1985) was a British mathematician and World War II codebreaker at Bletchley Park. Welchman envisioned an enhancement to Alan Turing's design for electromechanical codebreaking machine, the bombe. Welchman's enhancement, the "diagonal board" rendered the device practical enough to break messages sent with the German Enigma machine. Bombes became one of the primary tools used to decipher Enigma during the war. June 15 is the 166th day of the year in the Gregorian calendar (167th in leap years), with 199 days remaining. ... 1906 was a common year starting on Monday (see link for calendar). ... October 8 is the 281st day of the year (282nd in leap years). ... 1985 is a common year starting on Tuesday of the Gregorian calendar. ... World War II was a truly global conflict with many facets: immense human suffering, fierce indoctrinations, and the use of new, extremely devastating weapons like the atom bomb. ... Cryptanalysis (from the Greek kryptós, hidden, and analýein, to loosen or to untie) is the study of methods for obtaining the meaning of encrypted information without access to the secret information which is normally required to do so. ... During World War II, British and American cryptographers at Bletchley Park broke a large number of Axis codes and ciphers, including the German Enigma machine. ... The Bombe replicated the action of several Enigma machines wired together. ... In the history of cryptography, the Enigma was a portable cipher machine used to encrypt and decrypt secret messages. ...

Welchman was appointed head of Hut Six, the section at Bletchley Park responsible for breaking German Army and Air Force Enigma.

References

• Gordon Welchman, The Hut Six Story: Breaking the Enigma Codes, revised edition: M & M Baldwin December 1997, originally published 1982. ISBN 0947712348.