After Poland fell in 1939, the same mathematicians who first cracked Enigma continued their work in secret from this French château until Germany invaded again.
Paternel 1, CC BY-SA 4.0
The Bruno Intelligence Station
In the autumn of 1939, the Château de Vignolles, located about 40 kilometers southeast of Paris, became the clandestine site of one of the most important intelligence operations of World War II. Code-named PC Bruno, this Polish-French signals intelligence station housed the core of the Polish Cipher Bureau, which had been evacuated just weeks earlier during the invasion of Poland. The team included the three mathematicians who had first broken the German Enigma cipher in December 1932: Marian Rejewski, Jerzy Różycki, and Henryk Zygalski.
Under the command of French Captain Gustave Bertrand, PC Bruno was a multinational effort. The staff consisted of about 15 Polish cryptologists and technicians, 50 French personnel, and a small team of seven anti-fascist Spaniards who concentrated on Italian and Spanish ciphers. The Polish team, known as "Team Z" or "Source Z," arrived and resumed their work on October 20, 1939. Their mission was to continue the cryptanalysis of German military communications, a task they had mastered for nearly seven years before the war. The intelligence provided by a German spy, Hans-Thilo Schmidt, to French intelligence in the early 1930s had helped with the Poles' initial success, and this collaboration now continued on French soil.
Resuming the Code War
From the relative safety of the château, the Polish team picked up where they had left off. Working closely with their new British counterparts at Bletchley Park, the codebreakers at PC Bruno successfully decrypted several thousand Enigma messages between late 1939 and the spring of 1940. The two centers, Bruno and Bletchley, shared the workload and the results, each decrypting about half of the successfully intercepted traffic.
The information gleaned from these decryptions provided important, though often unheeded, warnings. The team uncovered intelligence foretelling the German invasions of Denmark and Norway in April 1940, and later, the offensive against Belgium, the Netherlands, and France itself. In January 1940, they broke back into the German Enigma network, repeating their pre-war success and providing the Allies with an intelligence advantage. The operation at Château de Vignolles continued at full pace until the German advance on Paris became unstoppable. On June 10, 1940, just after midnight, Bertrand evacuated the entire staff. The core Polish and Spanish personnel were flown to Algeria on June 24, escaping just two days after France's surrender. Their work would continue later in secret from "PC Cadix," a new clandestine station near Uzès in the unoccupied Vichy zone.
💡Fun Facts
The facility's codename, PC Bruno, was chosen by the French. "PC" is an abbreviation for "Poste de Commandement" (Command Post).
Before fleeing Poland, the Cipher Bureau shared all of its Enigma-breaking techniques, including designs for the "cryptologic bomb" and "Zygalski sheets," with French and British intelligence in July 1939.
After their second evacuation from Vichy France in 1942, Rejewski and Zygalski eventually made it to Britain but were assigned to solve low-grade German ciphers, their true expertise largely unused by the British.
Jerzy Różycki, one of the three original Polish mathematicians, did not survive the war; he died in January 1942 when his ship, returning to France from Algeria, sank in the Mediterranean.
