ABSTRACT
The use of radio communications in warfare makes cryptography important. Anyone can receive the messages, but the sender wishes them to be understood only by the intended recipient. The importance of cryptography accordingly became apparent in World War I, and the British Government Code and Cypher School (GC&CS) was set up in 1919.1 In 1939, it was transferred to Bletchley Park, an undistinguished, moderately-sized Victorian country house conveniently situated for rail access from London, Oxford and Cambridge.
