(William) Gordon Welchman (June 15, 1906, Bristol, England – October 8, 1985, Newburyport, Massachusetts, USA) was a British mathematician, university professor, World War II codebreaker at Bletchley Park, and author.
Education and early career
Gordon Welchman was educated at Marlborough College and then studied Mathematics as a scholar at Trinity College, Cambridge from 1925 to 1928. In 1929, he became a Research Fellow in mathematics at Sidney Sussex College, Cambridge, a Fellow in 1932, and later Dean of the College.
At Bletchley Park
Just before World War II, Welchman was invited by Commander Alastair Denniston to join the Government Code & Cypher School at Bletchley Park, in case war broke out. He was one of four early recruits to Bletchley (the others being Alan Turing, Hugh Alexander, and Stuart Milner-Barry), who all made significant contributions at Bletchley, and who became known as 'The Wicked Uncles'. They were also the four signatories to an influential letter, delivered personally to Winston Churchill in October 1941, asking for more resources for the code-breaking work at Bletchley Park. Churchill responded with one of his 'Action This Day' written comments.
Welchman envisaged an enhancement to Alan Turing's improved design of the Polish electromechanical Enigma-cipher-breaking machine, the bombe. Welchman's enhancement, the 'diagonal board', rendered the device substantially more efficient in the attack on ciphers generated by the German Enigma machine. Bombes became the primary mechanical aid in breaking Enigma ciphers during the war, by speeding up the search for current wheel order settings being used with the Enigma machines; these were changed often, initially at least once per day.
Welchman was head of Hut Six, the section at Bletchley Park responsible for breaking German Army and Air Force Enigma ciphers. In 1943, he became Assistant Director in charge of mechanisation, and also had responsibility for cryptographic liaison with the USA.
After World War II
Welchman moved to the United States in 1948, and taught the first computer course at MIT in the United States. He followed this by employment with Remington Rand and Ferranti. He became a naturalised American citizen in 1962. In that year, he joined the MITRE Corporation, working on secure communications systems for the US military. He retired in 1971, but was still retained as a consultant. In 1982 his book The Hut Six Story was published by McGraw-Hill in the USA, and by Allen Lane in Britain. The National Security Agency disapproved. The book was not banned, but Welchman lost his security clearance (and therefore his consultancy with MITRE), and was forbidden to discuss with the media either the book or his wartime work. Welchman died in 1985. His final conclusions and corrections to the story of wartime codebreaking were published posthumously in 1986 in the paper 'From Polish Bomba to British Bombe: the birth of Ultra' in Intelligence & National Security, Vol 1, No l. The entire paper was included in the revised edition of The Hut Six Story published in 1997 by M & M Baldwin.
- Greenberg, Joel (2014). Gordon Welchman: Bletchley Park's Architect of Ultra Intelligence. Frontline Books. ISBN 978-1848327528.
- Denniston, Robin (2004). "Welchman, (William) Gordon (1906–1985)". Oxford Dictionary of National Biography (Oxford University Press).
- Welchman, Gordon (1984) . The Hut Six story: Breaking the Enigma codes. Harmondsworth, England: Penguin Books. ISBN 0-14-00-5305-0. An early publication containing several misapprehensions that are corrected in an addendum in the 1997 edition.