Military Intelligence History: Ciphers in WWII ENIGMA and SIGABA.


I wrote an article for Yahoo! a few years ago (that I intend on updating this year) that proposed the top five intelligence victories that turned the tide of war. The ENIGMA story is arguably one of the most significant of these victories. I have yet to see The Imitation Game (it’s on the list!), but from what I understand, it omits quite a bit of the intelligence work (and luck) that went into breaking the unbreakable code. Cracking Enigma took a combination of old fashioned spy work, signals collection (meaning the interception of radio transmissions), and cryptography. Polish breakthroughs combined with a German traitor (provided by the French) resulted in the first successes against Enigma. The British and Americans were able to expand this success into breaking the even more resilient Enigma machines used by the German Navy.

These photos were taken at the National Museum of the US Air Force.

Pic 1: SIGABA – SIGABA was a US cipher machine based on the electromechanical rotor principle. It was developed in the late 1930s as a joint effort of the US Army and Navy [1]. At the time it was considered a superior cryptomachine, intended to keep high-level communications absolutely secure. It was used throughout WWII and was so reliable that it was used well into the 1950s, when it was replaced by machines like theKL-7. As far as we know, SIGABA was never broken. (


Pic 2: ENIGMA – The Enigma machine is an electro-mechanical device that relies on a series of rotating ‘wheels’ or ‘rotors’ to scramble plaintext messages into incoherent ciphertext. The machine’s variable elements can be set in many billions of combinations, and each one will generate a completely different ciphertext message. If you know how the machine has been set up, you can type the ciphertext back in and it will unscramble the message. If you don’t know the Enigma setting, the message remains indecipherable. (


For an awesome introduction to ciphers and the workings of ENIGMA, check out Tony Sales’s Ciphers and Codes at

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