Many people know the story of Alan Turing and his work at Bletchley Park in designing the British bombes, the machines used to crack the German Enigma codes. What most people don’t know is what happened afterward. When the German military added a fourth rotor to the Enigma, a new type of machine was needed in order to crack the codes and keep Allied intelligence out of darkness. These American bombes were the first multifunction computers ever built, and are an important part of the history of modern computing. It’s the incredible, gripping story of an enterprise that rivaled the Manhattan Project in secrecy and complexity, and ultimately led to the first modern digital computer.