This is the coded text of the Zimmermann telegram written by the German foreign minister Arthur Zimmermann to the German ambassador in Mexico in 1917 The full text of the telegram was published in the U S press on March 1 1917 Zimmermann himself admitted that he had written it The impact on American public opinion was immediate and just over a month later on April 6 1917 the U S Congress declared war on Germany and its allies A NEW MACHINE From World War I onward a new technology sending
messages by radio required new levels and techniques of secrecy In 1918 a Swiss businessman Arthur Scherbius invented a machine to encrypt turn into cipher messages He sold it to banks and businesses as a security tool and called the machine Enigma The German armed forces began to use a military version of Enigma in 1926 So Enigma was not just one machine it was a type of machine and many Enigma machines were manufactured over the following decades SETTING THE SCENE It is important to remember that all the events described in this book happened before the computer age when the main forms of communication were radio and telephones with landlines and all records had to be kept on paper HOW DID ENIGMA WORK The Germans believed their Enigma ciphers were uncrackable They continued to believe this throughout World War II The British and Americans were incredibly careful about how they used intelligence gained from deciphered Enigma codes in order to keep the Germans using Enigma What was it about this machine that gave the Germans such faith Scherbius’s machine looked a bit like a typewriter with a keyboard When the operator pressed a letter on the keyboard the action moved rotors called scramblers Once a letter was
coded its cipher lit up on a lampboard The rotors moved every time a key was pressed so the same letter would be enciphered differently To decipher an Enigma message the receiving operator needed to know the starting settings of the scramblers in the sending machine as well as which rotors had been used and in which order With this information key and an Enigma machine it was possible to unscramble the message The Germans set daily keys which were distributed in codebooks This is why the capture of codebooks and Enigma machines was so important to the Allied code-breaking effort
Rotor Rotor adjuster Lampboard Start here Keyboard Plugboard This diagram of the Enigma machine shows the route of encryption from keyboard to plugboard through the rotors and back WHAT DID THE ALLIES USE Both British and American cryptographers developed their own cipher machines The British adapted a commercial version of Enigma in 1934 to produce a machine known as
