Turing’s Machine 213

Turing’s Machine 213 Thanks to Turing’s insight into coding schemes and the machines he designed, the British were soon able to read almost every coded message the Germans sent during the war, giving the Allies an enormous advantage. The D-Day invasion involved convincing Hitler that the Allies had a huge army of nearly 400,000 men, massed around Dover preparing an attack on Calais head on, with a second army in Scotland poised to attack Norway. In truth, they had only 150,000 men planning an assault on the Normandy Beaches in the South. Just before the landings messages were decoded showing Hitler had fallen for the Allied subterfuge. Even as the Normandy landings began, Hitler still thought this a bluff and kept his 28 divisions at Calais waiting for the imagined attack. Without this intelligence advantage, the Allies would have needed a much larger invasion force, and Churchill believed Turing’s work shortened the war by as much as two years. The cracking of Enigma remained a secret after the war and Turing’s story remained untold for many years. When Churchill wrote his history, The Second World War, a massive work in six volumes, all sorts of sensitive information featured, but Turing’s work was omitted. One sentence hints that Churchill might write something about it in the future, but he never did. Churchill considered the work at Bletchley Park so sensitive he had it put in the highest classification — extending the 30-year secrecy rule. We must presume the decoding schemes were still being deployed during the Cold War. The papers were finally released in 2010. In one of those sad turns in history Turing was found guilty of gross indecency for homosexuality in 1954, a criminal act at the time, and was prescribed hormone treatment. This affected his mental state and he took his life by eating an apple laced with cyanide. He was eventually honored posthumously as a war hero and one of the most significant thinkers of the 20" Century. A Turing Award is the equivalent of the Nobel Prize for Computing. He was given a royal pardon in 2013. To see how Turing came up with the idea for the Turing machine and solved the decision problem, we need to get a feel for theoretical mathematics. That might sound a little heavy going but don’t worry, I will use a simple piece of mathematics to explain, one we have all played with as children, secret codes. HOUSE_OVERSIGHT_015903