If you're not familiar with the story, the Germans started using Enigma in 1932 to encrypt their sensitive military communiques and the Poles cracked it later that year; but the Germans kept refining the device and improving the cryptography. By 1939, the Poles had been overrun by the Nazis and were out of the game and Enigma's encryption was practically unbreakable as long as the German operators were using the machine correctly. The British took up the charge but couldn't decipher more than a tiny trickle of German Enigma messages.
The British Government launched a top secret effort, later codenamed "Ultra," to beat the machine. Turing was one of the mathematicians recruited from Cambridge University for the effort and developed much of the "bombe" technology that ultimately defeated Enigma. Sir Harry Hinsley, official historian of British Intelligence in World War II, said that Ultra's success in breaking Enigma shortened the war "by not less than two years and probably by four years." Sir Winston Churchill was even more definitive about Ultra's contribution, telling King George VI that "It was thanks to Ultra that we won the war."
In the process of developing the technology to defeat Enigma and helping save the free world from the Axis, Turing also made several breakthroughs that made modern computers possible. That desktop/portable device you're using to read this post? You can thank Alan Turing for it.
But Alan Turing was also gay. Homosexual acts were illegal in the UK in the 40s and 50s, and Turing was prosecuted for gross indecency. He accepted chemical castration as an alternative to prison and the British government stripped his security clearance. He was found dead in 1954 at age 41, and the autopsy ruled that he had committed suicide by ingesting cyanide. In 2009, UK Prime Minister Gordon Brown issued a formal apology for "the appalling way he was treated"; and Queen Elizabeth II granted Turing a posthumous pardon on Christmas Eve 2013...an especially meaningful gesture when you realize that Turing was charged the very same month that Elizabeth began her reign (yes, she's has been on the throne that long).
It's a fascinating story and the movie is receiving rave reviews at pre-release screenings – Benedict Cumberbatch as Alan Turing and Keira Knightley as Joan Clarke? Yes, please. If you're a fan of espionage thrillers or movies like A Beautiful Mind, go see this one on opening day, 14 November 2014.