Delilah—encrypting speech

Once Enigma was solved and the pioneering work on Tunny was done, Turing’s battering-ram mind was needed elsewhere. Routine codebreaking irked him and he was at his best when breaking new ground. In 1942 he travelled to America to explore cryptology’s next challenge, the encryption of speech. Turing left Bletchley Park for the United States in November 1942. He sailed for New York on a passenger liner, during what was one of the most dangerous periods for Atlantic shipping. It must have been a nerve-racking journey. That month alone, the U-boats sank more than a hundred Allied vessels. Turing was the only civilian aboard a floating barracks, packed to bursting point with military personnel. At times there were as many as 600 men crammed into the officers’ lounge—Turing said he nearly fainted. On the ship’s arrival in New York, it was decreed that his papers were inadequate, and this placed his entry to the United States in jeopardy. The immigration officials even debated interning him on Ellis Island. ‘That will teach my employers to furnish me with better credentials’ was Turing’s laconic comment. It was a private joke at the British government’s expense: since becoming a codebreaker in 1939, his employers were none other than His Majesty’s Foreign Office. America did not exactly welcome Turing with open arms. His principal reason for making the dangerous trip across the Atlantic was to spend time at Manhattan’s Bell Telephone Laboratories, where speech encryption work was going on, but the authorities declined to clear him to visit this hive of top-secret projects. General George Marshall, Chief of Staff of the US Army, declared that Bell Labs housed work ‘of so secret a nature that Dr. Turing cannot be given access’. While Winston Churchill’s personal representative in Washington, Sir John Dill, struggled to get General Marshall’s decision reversed, Turing spent his first two months in America advising Washington’s codebreakers—no doubt this was unknown to Marshall, who might otherwise have forbidden Turing’s involvement. During this time Turing also acted as consultant to the engineers who were designing an electronic version of his bombe for production in America.