Code-breakers: Secret War

Meet Christine. It’s her first day as a translator working at Bletchley Park in Buckinghamshire, UK. It’s your first day too, and you walk in together. Christine has travelled 50 miles north of London, which suffers nightly bombing raids because it’s 1941 and Britain is at war with the Nazis.

It’s comparatively tranquil here, as you walk towards the hut where you’ll work. You wonder why you had to sign the Official Secrets Act.

The buildings are hidden in the trees – probably to protect them from being spotted by enemy aircraft. 

Hut 3 is the building you will work in. You speak fluent French and German and have an excellent academic history. Your new place of work looks dull on the outside, but inside is a hive of activity, with many people busy at their desks. 

Your shifts this week are 08.00–16.00, but Bletchley Park operates 24 hours a day, with shifts from 16.00–00.00 and 12.00–08.00. It doesn’t have the time to stop.

This is the inside of your hut, where you will do your translations. It is quiet and everyone is concentrating: people work with an intensity and sense of urgency because they know that the messages that they translate could save lives if they do it quickly enough. 

You’ve translated a lot of messages today, but this one seems more important than the others. It appears to be the coordinates of a position in the Atlantic Ocean, sent from a German U-boat.

Before messages could be translated, the code – or cipher – had to be cracked. Alan Turing was one of those employed to crack codes, and ran Hut 8 along with Hugh Alexander.

Alan Turing studied mathematics at Cambridge University and wrote his doctoral thesis at Princeton University. 

In 1936 he wrote a paper called “On Computable Numbers”, where he described a “universal machine” that heavily influenced much of the development of computing as we know it today. He joined Bletchley Park on the first day of the war.

The rotors inside the Enigma machine were reset each day, which meant that if you didn’t crack the code in 24 hours, you had to start again. There were also plugs at the front of the machine that could be changed to further complicate the message. 

The operators all needed to know exactly what the settings for each day were.

Alan Turing and Gordon Welchman took inspiration from Polish codebreakers, designing a machine that could work out possible combinations of letters by running many drums at once, like the rotors found in Enigma machines. 

At its peak, over 200,000 messages a day were processed at Bletchley Park by a close-knit, intelligent, hardworking team. We now know that the workers there probably shortened the Second World War by 2 years.