Bletchley Park had been compiling vital intelligence for Allied commanders for over 18 months in the run up to D-Day, but the Codebreakers also supported the operation as it unfolded.
Notably, around the date of the invasion (May-July 1944), Bletchley Park took the risk of intercepting enemy messages directly on site in order to speed up the codebreaking process. Secret listeners in Hut 18 (formally Hut 8) were monitoring German Enigma traffic round the clock to monitor the response to the invasion, as well as any threats to the invasion fleet at sea, and the movement of troops in northern France – so that nothing was left to chance. By D-Day, the 7,000 strong workforce at Bletchley Park were decrypting almost 5,000 Enigma messages a day.
The pages below should give a powerful sense of what it was like to be at Bletchley Park during this time, following the progress of the Normandy landings through the reactions of the Germans to the long-anticipated invasion.