University, joined the GC&CS at the outbreak of hostilities with Germany. In early September 1939, the mathematicians reported to the new home of GC&CS, a Victorian manor in Bletchley, England, known as Bletchley Park (BP). They received a briefing on the work of the Polish Cipher Bureau and the Polish mathematicians. Turing and Welchman individually began thinking of ways to more quickly solve the German Enigma messages. They would both play a crucial role in the development of the cryptanalytic machine.

Alan Turing realized that the solution did not lie in creating a machine that replicated sixty Enigmas. The Polish Bomba searched for matches in indicators. Once already the Germans had changed how indicators were used, throwing the Poles back into the darkness until new Zygalski sheets could be cut. The Germans could easily change the indicators again. Turing began thinking about a machine that worked, not with the indicators, but with assumed text. By using text that cryptanalysts assumed appeared in the message, the machine would not be dependent on the indicators.

Like the Polish Bomba, the machine Turing conceived would also run through all the possible settings. Rotors and wires would simulate a series of Enigma rotors and pass an electrical current