Enigma I rotor cipher machine with 3 rotors

In the First World War, the German military still encrypted by hand, meaning that the enemy could read most of their messages. Consequently, the Wehrmacht used ciphering machines from 1930. The Enigma machine appeared to be indecipherable with its 100 quadrillion combinations. During the Second World War, the German armed forces had complete faith in the ingenious design of the Enigma machine—even though some of the enemy's unexplained successes should have given rise to doubt.