Secret British decrypting center. Just prior to the beginning of World War II, the British Government Code and Cypher School (GC&CS) purchased a Victorian mansion known as Bletchley Park (BP, also called Station X or War Station), located some 50 miles north of London in Bedfordshire. British code-breakers, some of them veterans of World War I, began moving to Bletchley Park in August 1939. The staff, headed by Alistair Dennison, soon numbered 150 people. Thereafter, BP grew very rapidly. By late 1942, BP personnel numbered around 3,500, a figure that would expand to 10,000 by 1945. BP's overseas stations were the Combined Bureau, Middle East; the Wireless Experimental Centre at Delhi; and the Far East Combined Bureau. Each had its own outposts.

The personnel at Bletchley Park were a mix of mathematicians, cryptographers, engineers, and eccentrics. Among them was Alan Turing, regarded as the father of the modern computer. There were also members of the various British military services, as well as foreign military personnel. At BP, they continued the work begun by the Poles in reading German signals traffic and unlocking the secrets of the German Enigma encoding machine.

To house the growing staff, "temporary" wooden huts were built on the garden grounds. These were numbered, and different types of analysis were conducted in each. Hut 3 decrypted German army and air force codes, Hut 6 focused on German army and air force Enigma cryptanalysis, Hut 4 worked on German naval translating and processing, and Hut 8 handled German navy Enigma cryptanalysis. Others worked on Italian and Japanese codes. The intelligence produced by BP was code-named the ultra secret.

By 1940, Bletchley Park had come up with additional devices that, given time, could sort through the possible variations of an encoded text. Careless German practices, mostly in the Luftwaffe, gave the electromechanical devices called "bombes" a head start and greatly shortened the delay between receiving and decoding messages. The changeable settings of the Enigma machine meant that most messages could not be read in real time, but the information was nonetheless invaluable.

The staff at BP was ultimately able to provide an important advantage to the Allies in the war. The Axis powers never learned of the success of the Allied decrypting operations, and the activities at Bletchley Park remained unknown to the public until 1974, when Group Captain F. W. Winterbotham revealed them in his book entitled The Ultra Secret.

A. J. L. Waskey

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Further Reading
Friedman, Maurice. Unraveling Enigma: Winning the Code War at Station X. South Yorkshire, UK: Leo Cooper, 2001.; Hinsley, F. H., and Alan Stripp. Code Breakers: The Inside Story of Bletchley Park. New York: Oxford University Press, 1994.; Lewin, Ronald. Ultra Goes to War. New York: McGraw-Hill, 1978.; Winterbotham, F. W. The Ultra Secret. New York: Harper and Row, 1974.