During the Drumbeat crisis and the codebreaking "blackout" of 1942, Allied intelligence leaders like Edward W. Travis established close ties with influential U.S. Navy intelligence officials like U.S. Navy Commander Joseph N. Wenger. A veteran Royal Navy intelligence officer, Travis was then serving as director of the British Government Code & Cypher School (GC&CS). Like Travis, Wenger was well-experienced in intelligence operations. In 1942, he headed the War Plans section of the U.S. Navy Operations Branch 20, Communications Intelligence Subsection G (OP-20-G).
Formally holding relatively junior military ranks, Travis and Wenger were given the authority to negotiate the definitive Anglo-American agreements that enabled Allied codebreakers to cooperate at solving German and Japanese codes and ciphers. In the summer and fall of 1942, Travis and Wenger placed a high priority on solving the M4 Enigma. Though technologies like RADAR, HF/DF, and SONAR offered a limited means of locating U-boats in the vastness of the open sea, "very special intelligence" derived from the deciphered text of Axis radio messages often provided long-term insights into enemy plans and objectives. Therefore, when Travis and Wenger formally agreed to streamline Allied intelligence-gathering efforts, Anglo-American codebreakers could effectively pool their intellectual and technical resources to solve the M4 Enigma. The BombeTo decipher Enigma cryptograms, British codebreakers used a machine known as the Bombe. Originally conceived by Polish codebreakers in the late 1930s, the term "Bombe" is loosely derived from the original Polish reference to the loud ticking noises that the machine produced while processing Enigma messages. In general, the device operated on electromechanical principles similar to those of the Enigma. Bombe machines rejected thousands of inconsistencies within a given Enigma message, thus providing a means of solving some characters in an Enigma cryptogram. Frequently, the Bombe revealed enough information to deduce the circuitry settings of the enemy Enigma machine. Allied cryptanalysts could then review and reprocess the text and likely solve the Enigma cipher settings. Thus, the enciphered text of a given Enigma cryptogram could be solved to reveal the true text of the intercepted message. During the war, Bombe machines were essential tools in Anglo-American intelligence-gathering efforts against Axis forces. Without significant Polish and French assistance, however, the Anglo-American Allies would have experienced greater difficulty in developing a mechanical means of penetrating the Enigma cipher in the early years of the war. In the months following the German offensive of September 1939, both French and Polish intelligence operatives filtered key information about the Enigma system to GC&CS. Using this information, British cryptanalysts developed an improved Bombe that could process Enigma messages more efficiently than the original Polish design. British codebreakers, most notably Alan S. Turing, also applied some fundamental principles of cryptanalysis to streamline the Bombe process using "cribs" and "cillies" —codebreaker's slang for textural clues that often appeared in encoded messages. Using Bombe machines to identify cribs and cillies, codebreakers found breaching points in the Enigma cipher to solve portions of enemy messages more quickly. Once portions of an enemy message were identified, cryptanalysts could often exploit the breach to decipher the rest of the enemy communication. Page 1 of 2 | Next >>
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