One of the great Allied advantages over Nazi Germany during World War II was their ability to regularly intercept and read otherwise encoded German communications. Though this capability was not comprehensive, with changes to the German code settings throwing the Allies off at repeated times during the war, it proved of significant assistance to the Allied war effort. Some believe Allied code-breaking efforts were so consequential as to have decisively altered the course of the war.
The central location for Allied code breaking efforts was at Bletchley Park, northwest of London.
An actual Second World War Enigma machine, used by Germany to encode its communications, was auctioned by Christie's on September 29, 2011. An electro-mechanical rotor cipher machine used to encrpyt and decrypt messages the Enigma was thought to be unbreakable, but of course it was not.
One of the great Allied advantages of the war was their ability to regularly intercept and read otherwise encoded German communications.