What was PC Bruno?

PC Bruno was a Polish/French signals intelligence station near Paris during World War II, from October 1939 until June 1940.

Its function was decryption of cipher messages, most notably German messages enciphered on the Enigma machine. PC Bruno worked in close cooperation with Britain's decryption centre at Bletchley Park.

In the early 1930s, French military intelligence acquired operation manuals and sample messages for the German Enigma cipher machine.

French intelligence officer Captain Gustave Bertrand supplied this material to Poland's Biuro Szyfrów ("Cipher Bureau"), which used it as part of their successful effort to break Enigma.

In July 1939 the Biuro Szyfrów gave French and British intelligence all their results. Both countries were expanding their decryption efforts in anticipation of war, and this continued after the war started in September 1939.

When Poland was overrun by Germany and the Soviet Union, the key staff of the Biuro Szyfrów were evacuated to Romania, and from there eventually reached France. In October 1939 the Poles resumed work, hosted by French intelligence at PC Bruno.

By June 1940, advancing German forces were approaching PC Bruno. Just after midnight on 10 June, Bertrand evacuated the Bruno staff from Gretz-Armainvillers. France surrendered on 22 June; on 24 June he flew the 15 Poles and seven Spaniards in three planes to Algeria.