Alongside the loud, explosive, and visible battles of the Second World War, another war was being fought. It was a silent, secret conflict waged not with bullets and bombs, but with mathematics and machines. It was a war of codes and ciphers, a battle of minds hidden away in the English countryside, and its outcome was just as crucial to the fate of the world. At the center of this secret war was one of the greatest minds of the 20th century: Alan Turing.