World War II Code-Breakers
In the summer of 1939, with war looming, British cryptanalysts of the Government Code and Cipher School were evacuated to Bletchley Park, a Victorian mansion located about 50 miles from London in Buckinghamshire. It was headed by a naval officer, Commander Edward Travis.
By listening to the ever-increasing German radio traffic, it was estimated that a huge number of people would be required to deal with the material in the decoded intercepts from Enigma and other German ciphers.
Radio operators were taken on at various sites to intercept enemy radio traffic, while Bletchley Park took on WRNS (Women’s Royal Naval Service) personnel to act as decoding clerks, engineers, mathematicians and intelligence experts.
A total of 10 000 people worked at Bletchley, at various locations scattered around Britain and with the Allied armies in the field. The analysed material they dealt with from Enigma, later Axis machines, and German hand ciphers was known as Ultra.
At first, most radio traffic was generated by the Enigma machine. Each of the German services used a different model of it and devised its own codes and procedures. Despite help in the early stages from Polish intelligence agents and the occasional captured code book, it took time to break the ciphers. The principle aid for deciphering Enigma traffic, which Alan Turing helped to develop, was the ‘bombe’.
Alan Turing was an early Bletchley Park recruit. In 1936 he had published a paper, “Computable Numbers”, now recognised as the theoretical basis of the modern computer. In July 1939, as a member of the British delegation that went to Poland, he was given complete details of the Polish bomba. These bombas, machines originally developed in Poland, penetrated the German Enigma ciphers in extensive trials by working at a few characters a second.
Turing worked on a much improved British version - the ‘bombe’ - to which he contributed his considerable knowledge of mathematics and mechanical engineering. The bombe developed by the Bletchley team was an electromagnetic relay machine named the ‘bronze goddess’. It stood eight feet high and had wheels corresponding to the rotors of the Enigma together with other complicated circuits. It was essentially an Enigma machine in reverse, but much more complex.
T H (Tommy) Flowers was the chief architect of Colossus, the code-breaking electronic computer used at Bletchley. Flowers joined the Post Office Research Station at Dollis Hill in 1930. His major research interest was long-distance signalling, especially in transmitting control signals to replace human telephone operators with automatic switching equipment.