Women Were Key to WWII Code-Breaking at Bletchley Park

Female operators and mathematicians play a greater role in the history of computers and code-breaking than most realize

Bombe machine drum
Jean Valentine, a former Bombe machine operator, shows a drum of the machine in Bletchley Park Museum in Bletchley, England. ALESSIA PIERDOMENICO/Reuters/Corbis

The Imitation Game has brought to popular culture the story of Alan Turing—the WWII codebreaker who cracked the Enigma code, proposed a now-famous test of computer intelligence and was convicted, in a sad example of homophobia, of "gross indecency" for being gay. (He has at last been pardoned.) The film also features Joan Clarke, one of few women to work as a codebreaker at Bletchley Park and Turing’s friend. But Clarke was not the only women at the Park. For The Conversation, Bryony Norburn writes, "At its height there were more than 10,000 people working at Bletchley Park, of whom more than two-thirds were women."

Most of the women were hired to do clerical work or assigned to monotonous tasks that were nevertheless key to the job at hand. Norburn writes:

Women held numerous roles at Bletchley, ranging from administrators, card index compilers and dispatch riders to code-breaking specialists. Initially the men in charge had assumed that women were incapable of operating the Bombe cryptoanalysis machines and later the Colossus code-breaking computers – until a group of Women’s Royal Naval Service (Wrens) were brought in. Proving themselves up to the job, many women who had signed up to travel and see the world in the navy instead found themselves assigned to “HMS Pembroke V” – the naval assignation for Bletchley Park – in deepest Buckinghamshire about 100 miles from the sea.

There they operated the code-breaking computers. Jean Valentine, who worked with the Bombe machines, tells her story in this video:

Operating the Bombe: Jean Valentine's story

Some women also cracked ciphers themselves. Margaret Rock worked on German and Russian codes. She was apparently described by Dilly Knox, who helped decrypt the Zimmerman Telegram during WWI, as "the fourth or fifth best in the whole of the Enigma staff." Other notable female codebreakers include Mavis Lever and Ruth Briggs.

The story of the women at Bletchley has remained, like much of the work at the Park, shrouded in secrecy. "Up until now the main focus has been on the male professors who dominated the top level at Bletchley," Kerry Howard, a researcher, told Joe Miller for BBC. Miller writes, "In order to find any information on the women involved, you have 'to dig much deeper'."

Their stories should be told, Norburn argues, to help inspire the next generation of computer scientists and engineers. After all, computer programing used to be "women’s work."

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