Joan Clarke, the cryptanalyst war-heroine, and the women of Bletchley Park (you never heard of)

Laura Vianello
Oct 27, 2015 · 5 min read

Even if you’re not a History Buff, D Day is a term that rings the bell, right? June 6th, 1944, the Allied troops land on Normandy to fight the Nazis and begin the (cleverly named) Battle of Normandy. This resulted in the liberation of Western Europe from Germany’s control and the eventual Allied victory. Hoorray!

What you may not know, is that there was an extensive intelligence effort behind this battle, most of which happened on Bletchley Park. This was the central cite of the UK’s GC&CS (Government Code and Cypher School), tasked to penetrate secret communications of the Axis Powers. Some historians have estimated that the work done by the British Intelligence at Bletchley Park shortened the war by two to four years, and was a key element to the Allies’ success.

Now: what if I told you that the Bletchley Park personnel was 75 % — 90% made up by WOMEN? And what if I told you that one of those women was part of the The Hut 8 team? Meet Joan Clarke, the woman who worked side by side with Alan Turing and Hugh Alexander on breaking the German cipher system Enigma (and succeeded). Plus, she eventually became the deputy head of Hut 8 and would become its longest living member.

Let’s break it down: the Germans had something called the Enigma Machine that encrypted their messages into code. It was believed (both by the Allies and the Axis) that this code was unbreakable. Why? Because the machine had so many variable elements that it could make billions of combinations, AND the settings were changed every day AND each military intelligence had their own specific settings. Not knowing the settings meant the chances of being able to decipher a message was an astonishing 150 million million million to one. So the ciphers had to be broken in real time before they were reset for the new day. Talk about a high pressure job, right? Churchill’s Government set the GC&CS with one main purpose: break the Enigma code. But breaking this code was not a single-man (or single-group) task: it required constant contribution from a large personnel (over 10,000 people) including, in addition to cryptanalysts, clerks, machine operators, and intelligence and communications workers.

Joan and the Hut 8 Team (I wish this pic was larger)

Joan had a double first degree in mathematics (she was denied a full degree by Cambridge because, until 1948, those were only awarded to men). She was recruited to the GC&CS by one of her former supervisors, G. Welchman. Within a few days after enrolling and doing some clerical work, Joan was promoted to Hut 8. This was a significant promotion, but because she was the first and only senior female cryptanalyst, bureaucracy had no protocols to give her a raise. Thus, she was classed as a linguist and from there on she filled the forms with “grade: linguist, languages: none” (and even then she was paid less than her male colleagues).

Naval Enigma (codenamed Dolphin) was more complex to break than the others, as there were more variables to the codes. The Hut 8 team worked on codes related to U-boats intelligence, that is, German ships hunting down (and sinking) Allied vessels carrying supplies and troops from the US to Europe. Britain at the time was importing half of its food and all of its oil from North America. After the German occupation of France, German ships had easy access to the Atlantic through the Bay of Biscay. The situation was dire: at one stage, Britain was only three days from running out of food.

Alan Turing had invented a new codebreaking technique called Banburismus that allowed to narrow down the possible code combinations from 336 to 20. Joan was not only the only female Banburist, but she was also one of the best. She devised a method of her own to speed up the technique. But to her surprise she was told she was using a technique called Dillysimus, devised in WWI (and it is thought that the reasons for not naming this improvement after Clarke were, certainly, sexist). Other women codebreakers included Mavis Lever, Ruth Briggs, Dilly Knox and Margaret Rock. But unfortunately little is known about their work as their contributions are hardly noted anywhere.

Most importantly, all this code-breaking and cryptanalysis resulted in the first programmable computer, Colossus — which was operated by women (click on that link for awesome then and now photos). Historical memory has not been fair to the civilians and service women of Bletchley Park. They are (and were at the time) commonly referred to as the ‘girls’ of Bletchley Park, and although they were mostly young and well-educated they were almost entirely in supporting positions and the high-rank personnel (a.k.a. the people that made the decisions) was entirely made up by men. On top of that, the extreme secrecy around War Intelligence has prevented formal research until recently, so we might have to wait before we see significant work about these war heroines.

Never the less: you have Joan and the women of Bletchley Park to thank for changing the History of the World AND the fact that you’re reading this on a computer!

This is the second on a series of articles about Women in History. Check out my profile or my blog for my previous article on Sor Juana and more!

Laura Vianello

Written by

= Social Media + History + Art + Fashion + Cartoons + Cats. Basically, I’m a huge nerd. And everyone knows nerd is the new cool. http://about.me/LauraVianello

Welcome to a place where words matter. On Medium, smart voices and original ideas take center stage - with no ads in sight. Watch
Follow all the topics you care about, and we’ll deliver the best stories for you to your homepage and inbox. Explore
Get unlimited access to the best stories on Medium — and support writers while you’re at it. Just $5/month. Upgrade