ENCYCLOPEDIA OF Espionage, Intelligence, and Security Volume ...

Bletchley ParkSEE ALSOWorld War IBletchley Park❚ ADRIENNE WILMOTH LERNERBletchley Park was the headquarters of the British MilitaryIntelligence Government Code and Cipher School duringWorld War II. Located fifty miles north of London, on thegrounds of the sprawling Victorian mansion for which itwas named, Bletchley Park employed 12,000 code breakersand staff. Bletchley Park cryptologists successfullybroke the major codes used by the German military andhigh command, creating the most advanced computingsources of the time with few resources. British cryptologistsalso aided United States efforts to break Japanesecodes. Intelligence information gathered from BletchleyPark is credited with significantly aiding the Allied wareffort and saving thousands of lives.The beginning of Bletchley Park. Although British MilitaryIntelligence employed code breakers during World War I,they failed to establish a permanent cryptology departmentin the inter-war period. In 1938, on the eve of WorldWar II, British Military Intelligence revived the cryptologydepartment. Drafting cryptographers from all disciplines,and heavily recruiting young men from Oxford and Cambridge,the first cryptology operations were established inLondon. The group’s main task was to correspond withforeign code breakers in allied nations and cull informationregarding their cryptology efforts against Germancodes.In the summer of 1939, British Intelligence moved thecryptology department to Bletchley Park, officially dubbedStation X because it was the tenth division of the intelligenceorganization. A cipher school was established onthe grounds to train new code breakers. As war was on thehorizon, a large number of women were trained for employmentat Bletchley Park. At the height of the war, threequartersof Bletchley Park staff were women. The focus ofoperations at Station X shifted to active code breaking. Bythe outbreak of World War II in September of 1939, BletchleyPark cryptologists had already made considerableprogress against some German diplomatic codes.Early code breaking efforts. During the two years of the war,British cryptologists decoded German communicationswith limited success. Older codes, used for low securitymessages, were readily identified and broken by the BletchleyPark team. Some newer codes were broken mathematically,but decoding and translating these messagesby hand proved an arduous task. By the time messagesEncyclopedia of Espionage, Intelligence, and Securitywere fully understood, the information they containedwas often outdated. Compounding the problem, theseintercepts contained very little useful intelligence information.Since the mid-1930s, the German governmenthad used complex cipher machines to disguise their mostimportant communications.The first great code breaking triumph at BletchleyPark came on August 30, 1941. A British “Y Station,” oneof the military listening stations that intercepted Germancommunications, picked up a depth, a repeat transmissionthat used the same settings on the cipher machine. Thisintercept was forwarded to Bletchley Park. Cryptologistsidentified as “fish,” the nickname for a message producedby the illusive Geheimschreiber cipher machine. Withintwo months, the Bletchley Park team broke the high-levelGerman code.To facilitate the processing of “fish” intercepts, BletchleyPark engineers borrowed an idea from plans the Polishintelligence service gave Britain before the war. Theyconstructed a machine that aided the deciphering of intercepts,nicknamed a “bombe” because of the low, roaringnoise it made while operating. The “bombe” constructedto decipher Geheimschreiber transmissions did help cryptographersto process intercepts more rapidly, but themachine required the exact synchronization of two papertapes for printing. The tapes often broke, and the machinehad to be reset. In addition, the start setting to processeach intercept, the original cipher settings used by theGermans to send the message, had to be calculated byBritish cryptologists by hand. The process was still toocomplex to yield decoded intercepts ready for immediatetranslation to be useful to intelligence and militarypersonnel.Operation Ultra: breaking the German Enigma machine. Most ofGermany’s high-level military messages were encodedusing a cipher machine called Enigma. The complex codeused not only a cipher, but also an overlaying encryptionto disguise the original text. The series of rotor wheels onthe Enigma teleprinter gave the machine an extraordinarynumber of code combinations. The Germans were soconfidant that the machine code was so nearly infinite inpossibilities that it could never be broken. However, variousintelligence services in neighboring nations had madeconsiderable progress breaking Enigma even before theoutbreak of the war. In Britain, efforts to break Enigmawere known as Operation Ultra.In the months preceding the German invasion ofPoland in 1939, Polish intelligence passed on to Britishintelligence information on their efforts to break Enigma.Most helpful was the information Polish spies gathered onhow the cipher machine operated, including sketches ofthe teleprinter and some of its components. With theinformation, Bletchley Park cryptologists found two keyweak links in the Enigma code. Enigma code prohibitedthat any letter be encrypted as itself, and German standardsof communication dictated that the same phrase131