Alan Turing was a brilliant mathematician and also a genuine war hero, not because he fought in combat, but because he did crucial work for the British government during World War II. Turing broke a number of German codes, including communications that had been scrambled by the Enigma machines. In 1945, King George VI awarded Turing the Order of the British Empire.
In the following years, Turing made numerous contributions to knowledge, including the domain of pattern recognition. Many people consider him the father of computer science. Since 1966, the Association of Computing Machinery has awarded the Turing Award, perhaps the highest distinction in all of computer science, for contributions "of lasting and major technical importance to the computer field."
Turing was gay, and in 1952, he was convicted of the criminal offense of "gross indecency" for a sexual act with a man. Upon conviction, he was asked to choose between imprisonment or probation, with the latter conditioned on acceptance of hormonal treatment, which would reduce his sex drive. He chose the latter. He lost his security clearance and his consulting position with the U.K. government. In 1954, he died, almost certainly of suicide.