For two operators to communicate, both Enigma machines had to be set up in the same way. The large number of possibilities for setting the rotors and the plugboard combined to form an astronomical number of configurations, and the settings were changed daily, so the machine code had to be "broken" anew each day.

Before 1932, the Cipher Bureau had succeeded in solving an earlier Enigma machine that functioned without a plugboard, but had been unsuccessful with the Enigma I, a new standard German cipher