Following the
German invasion of France in 1940, Veuve joined the
Free French Forces, in which he reached the grade of captain. He worked for the U.S.
Office of Strategic Services (OSS) and with the
Résistance in northern France, and as a parachutists' instructor in the United Kingdom. The OSS assigned him the codename
Joyeuse ("joyful"), after
Charlemagne's sword. In April 1944, with 120 other agents as part of
Operation Sussex, he was tasked with gathering
intelligence about enemy military installations, supply depots and troop movements in northern France, in preparation for the upcoming
Allied invasion. Deployed by
parachute near
Chartres, disguised as a postal worker, Veuve acquired and transmitted information about crucial enemy infrastructure, such as
Le Bourget airport, an oil refinery and an underground rocket factory. Over sixty messages were transmitted, which covered enemy movements at airfields, troop identifications,
V-I manufacturing plants, underground factories and important gasoline depots. Although no provision had been made for the transmission of intelligence by courier, he showed great initiative in getting through to London two pouches of very valuable information on a naval powder factory and an oil refinery, both of which were subsequently heavily bombarded by allied aircraft. To avoid
radiolocation of his signal, he emplaced himself close to a German military unit's transmitter. After the Allied invasion, Joyeuse shifted his operations further inland, on one occasion narrowly escaping an
SS raid with a bullet wound in his foot, while his two bodyguards (Louis Barrault and Pierre Gastaud) were captured and executed on 18 August 1944 in Aulnay Sous Bois. With the advancing Allied forces he eventually reached Germany, being one of the first Allied officers to reach the
Bergen-Belsen concentration camp. ==Post-war career==