Officially credited with shortening WWII by two years, there is even speculation that without Turing, the war could have been lost. He deciphered the German Enigma machine; so unbelievably complex that Germany had total confidence its codes, changed daily, could never be cracked.
Perhaps more than anyone else, Turing also contributed to development of the modern computer, as well as an early pioneer of artificial intelligence.
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Turing suicided out in 1954 age 42, persecuted by prevailing British anti-homosexuality laws of the day. He did it with a cyanide-laced apple, in such a way as to allow his mother to believe his death was accidental - which she did always believe, all her life.