PC Bruno was the code name for the intelligence station operated at a farmhouse in the west of France to which French cryptanalysts retired after Paris was captured by the Germans in 1940. PC Bruno did not function for long, as its director, Capitaine Gustave Bertrand, successfully shut it down when he thought the Gestapo were closing in.

In July of 1939, the Polish Military Cryptographic Bureau had turned over to French and British Intelligence substantial information about their break into the German Army's Enigma traffic. Both British and French put considerable effort into reading German Enigma traffic (Wehrmacht and Luftwaffe) as the War began in Poland, and during the phony war period before the Germans invaded France. Many of the Polish cryptographers managed to reach France and were assigned to PC Bruno. After it was set up, Bletchley Park and PC Bruno cooperated against the German message traffic with considerable success.

After PC Bruno was shut down, most of its personnel (including the surviving Poles) made it to Britain, where they continued to contribute to the effort against the Germans. None, however, went to Bletchley Park and continued to work on cryptanalysis of German traffic, including Marian Rejewski who had made the epochal first break into military Enigma in 1932/33.

References

• Battle of Wits, Stephen Budiansky, a one volume account of WWII crypto reflecting much recently declassified material
• Sir Harry Hinsley (ed), 4 volume account of British cryptography in WWII
• Code-Breakers, Sir Harry Hinsley (ed), a volume of recollections by some of those who worked in cryptography in the UK during WWII