The Enigma  code was cracked in 1941.

http://upload.wikimedia.org/wikipedia/commons/d/dc/Typical_Bletchley_intercept_sheet.jpg

Whenever a key was pressed, the machine substituted a different letter. It ran on electricity.

 The Enigma machine was developed in 1918 by the Germans. The Enigma machine was used until after WWII. The machine was used for 26 years.

The Enigma

The Enigma was a rotor machine that used a substitution cipher.

Arthur Scherbius invented the Enigma machine.