The three-rotor Enigma is the standard German electro-mechanical ciphering machine widely used in World War II. It derives from a 1918 patent by Dr. Arthur Scherbius and was bought out by the German military in 1929 and placed in service. Enigma in several variants was used by the German Navy, the Wehrmacht, the Luftwaffe, the state railroad system (who used a variant of the K Enigma with the notches swapped on rotors I and III, the Abwehr (intelligence) and the SS. Enigmas that were made in the 1930s and used by the military were used to hide the build-up of the German Army before WWII. This build-up was expressly forbidden by the Versailles treaty.
It was designed with a complex, interchangeable series of three rotors bearing the 26-character alphabet, a 'reflector' and a plugboard with movable connecting cords that connected pairs of letters. As an added precaution, the base or starting settings for the rotors was changed every 24 hours, according to pre-printed code books furnished in advance or supplied daily by courier. It has been calculated that the 3-rotor ENIGMA, with plugboard in use, made possible a total of 15 billion billion possible readings for each character.
Enigma was widely regarded by the Germans as too complex to be broken, but in the 1930s a team of Polish analysts (Marian Rejewski, Jerzy Rozycki and Henryk Zygalski) made remarkable progress in working out the machine's basic system, identified its vulnerabilities and succeeded in deciphering much of the encrypted German radio traffic. Their findings, including plans for very useful mechanical devices known as 'bombes', which aided in the decryption operation, were secretly passed on in 1939 to French and British investigators. An elite team of cryptanalysts, mathematicians and engineers including Alan Turing (1912-54) were established in a top-secret facility at Bletchley Park. For the rest of the war that legendary team's heroic and unstinting efforts gradually accomplished the seemingly insurmountable task of deciphering an enormous volume of encrypted communications. The critical intelligence deriving from their decipherment was dubbed ULTRA and was employed cautiously but to great effect during the war; some commentators credit ULTRA with shortening the war by some two years.
Very few Enigma machines survived the war and it is particularly unusual to find one that was made in the 1930s that remained in such good condition. During WWII many of the Enigma machines were destroyed in military actions; near the end of the war the Germans destroyed their remaining Enigma machines as they retreated rather than have them captured by the Allies. After the end of the war, Churchill ordered that all remaining Enigma machines were to be destroyed.
Since the Allied breaking of the Enigma codes was not revealed for 30 years, some surviving Enigmas were put into service for a second time after the war by the BMdi, the Bundesministerium der Innern (Federal Ministry of the Interior) or the BGS, the Bundesgrenzschutz or the BND (Bundesnachrichtendienst). The BMDi and the BGS used the Enigmas to encipher names and birthdays etc. of persons whom they caught trying to illegally cross the borders of Germany after WWII especially in the area of the border to the east and the BND used Enigmas in security and police work. These post-war German foreign intelligence agencies refurbished some of the few surviving Enigmas with new paint and maintained and used the machines for many years after the end of WWII and into the Cold War era.