The Enigma machine was used by the German navy, air force and army to send encrypted messages.

BBC: Bletchley Park Enigma code hut to be restored

Even while British code breakers were cracking the Enigma machine and altering the course of the war, Americans were developing one of the most secure, efficient forms of encryption, which was also one of the simplest.

FORBES: I've got a secret

Bletchley Park was the wartime home of the Government Code and Cypher School which broke the codes generated by the German Enigma machine, using the Bombe.

BBC: Bletchley Park Enigma code hut to be restored

Turing is celebrated for his work in deciphering messages encrypted by the German Enigma machine.

BBC: Suffolk

With the advent of the first electrical cipher, the German Enigma machine in 1918, cryptanalysis changed its fundamental character.

FORBES: I've got a secret

Below, on the battlefields of Europe, German intelligence officers made the same oath to another computer, the Enigma coding machine.

FORBES: Malone's Musings: Memorial Day 1999