Book excerpt: Along with breaking the Japanese diplomatic cryptosystem, usually referred to as "PURPLE," probably the greatest example of Allied cryptanalytic success in World War II was breaking of the German Enigma machine. This cryptodevice was used by all of the German armed forces as the primary cryptosystem for all units below Army level or the equivalent. As D-Day approached, other German cryptodevices, the SZ-42 and the various T-52 machines, assumed great importance since they were used by the higher commands of the German armed forces. Many references to these German machines in the histories fail to provide information on what they looked like or how they worked. Another group of cryptodevices, those invented by Fritz Menzer for the Abwehr (Counterintelligence), have received little or no notice in the literature and are unknown to the public. This brochure is an attempt to remedy both lacks.