The Industrial Scale of Secrecy
During World War II, this English country estate became the secret center for Allied codebreaking. Known as Station X, the Government Code and Cypher School (GC&CS) located here grew from a staff of about 150 in 1939 to nearly 10,000 people by 1945. This workforce, approximately 75% of which was female, worked on the challenge of breaking German military codes. The personnel came from diverse backgrounds, including university graduates in mathematics and physics, linguists, and even winners of a crossword puzzle competition held in The Daily Telegraph. Everyone signed the Official Secrets Act, binding them to a silence they maintained for decades after the war.
The primary targets were the German Enigma and Lorenz ciphers. The Enigma, an electromechanical rotor machine, was used for most military communications and had a staggering number of possible daily settings—approximately 159 quintillion. Initial breakthroughs against the Enigma were made by Polish mathematicians in the 1930s, who shared their findings with the British. This collaboration was the basis of Bletchley Park's success.
The Dawn of Computing
To combat the Enigma's complexity, mathematician Alan Turing and engineer Gordon Welchman designed the Bombe. This electromechanical device systematically searched for the correct rotor settings. The first Bombe, named "Victory," became operational on March 14, 1940. By the end of the war, over 200 Bombes were in use, operated primarily by members of the Women's Royal Naval Service (Wrens). These machines could find the daily Enigma key in a matter of hours, rather than weeks.
An even greater challenge was the Lorenz SZ42 cipher, used for high-level communications between Hitler and his generals. Breaking this far more complex 12-rotor cipher required a new kind of machine. Post Office engineer Tommy Flowers led the design of Colossus, the world's first programmable electronic digital computer. The Colossus Mark 1, operational in February 1944, contained 1,600 vacuum tubes. It read encrypted messages from punched paper tape at 5,000 characters per second. The improved Mark 2 had 2,400 tubes and was five times faster, becoming active on June 1, 1944, just in time for the D-Day landings. By the war's end, ten Colossus machines were operational, having decoded 63 million characters of German High Command's messages.