Source: Wikipedia. Pages: 58. Chapters: Enigma machine, Bletchley Park, Ultra, Lorenz cipher, Cryptanalysis of the Enigma, Magic, OP-20-G, Station HYPO, Japanese naval codes, Fish, Far East Combined Bureau, Beaumanor Hall, The National Museum of Computing, Siemens and Halske T52, German code breaking in World War II, Station CAST, United States Naval Computing Machine Laboratory, World War II cryptography, PC Bruno, Signals Intelligence Service, Reservehandverfahren, B-Dienst, Wireless Experimental Centre. Excerpt: Cryptanalysis of the Enigma enabled the western Allies in World War II to read substantial amounts of secret Morse-coded radio communications of the Axis powers that had been enciphered using Enigma machines. This yielded military intelligence which, along with that from other decrypted Axis radio and teleprinter transmissions, was given the codename Ultra. This was considered by western Supreme Allied Commander Dwight D. Eisenhower to have been "decisive" to Allied victory in World War II. The Enigma machines were a family of portable cipher machines with rotor scramblers. Good operating procedures, properly enforced, would have made the cipher unbreakable. However, most of the German armed and secret services and civilian agencies that used Enigma employed poor procedures. It was the poor operating procedures that allowed the cipher to be broken. The German plugboard-equipped Enigma that would become the Third Reich's principal crypto-system was reconstructed-with the aid of French-supplied intelligence material that had been obtained from a German spy-by the Polish General Staff's Cipher Bureau in December 1932. From then until the outbreak of World War II, the Poles held a monopoly in decrypting German military Enigma ciphers. In July 1939, as war drew near, the Polish Cipher Bureau initiated the French and British into its Enigma-breaking techniques and technology at a conference held in Warsaw. From this beginning, the British Government Code and Cypher School at Bletchley Park built up an extensive cryptanalytic facility that used manual methods and machines - "Bombes". Initially, the decryption was mainly of Luftwaffe and a few Army messages, as the German Navy employed much more secure procedures for using Enigma. Alan Turing, a Cambridge University mathematician and logician, provided much of the original thinking that led to the design of the Bombes and the eventual breaking of naval Enigma. However, when the German Navy introduced an Enigma version with