In late 1942, what remained of the French military was demobilized. Grosjean was released, decided to go to law school and settled in Paris. According to his personal papers, his memoir, and research conducted by his son
François Grosjean, Roger Grosjean was serving
Vichy France but was not a
collaborator. He publicly spoke against the Germans, considered stealing a German plane and flying to England, and his circle of friends included the
French Resistance fighter Marcel Degliame. However, by May 1943, he was socializing with known collaborators. One of them was Georges Montet, whose brother Lucien, aka Christian Martell, was a resistance fighter and a member of the Alsace fighter group (
No. 341 Squadron RAF). Georges Montet, who was likely a double agent, offered to get Grosjean a job as a
ferry pilot with
Lufthansa. Although how and when they met is unclear, Grosjean wrote that he spoke to a British
agent called "Richardson", who was working in
Wattignies in northern France. Richardson told Grosjean to take the position. Grosjean then joined the
Free French Air Force, obtaining a position through pre-arrangement by MI5. He was promoted to Lieutenant and given a position in the intelligence service. With the knowledge of MI5, but not the French, he was also writing coded letters to his handler in Barcelona. In January 1944, he was given permission to fly again. By March, the Germans had become aware that he was working for the British and he wrote that he was "condemned to death". Both his British and French colleagues no longer trusted him. His handler wrote that it was "necessary to ensure that he got no access to operational information of any kind and that he was as far away from the zone of operations as possible." He was then posted to North Africa—first
Algiers and then
Meknes, where he worked as an instructor on
P-39s. In case he fell into German hands, he was given the name François Perrin. He was then sent to the
Lille Air Base, then to Paris to work at the
Air Ministry. In late 1946, Grosjean completed his military career as a captain in the Air Force Reserves. The French government awarded him the
Croix de Guerre and the
Legion of Honour. He was also one of a few to receive the
Commemorative medal for voluntary service in Free France, and a hand-written note from General
Charles de Gaulle reading: "You answered France's call when it was mortally wounded by joining the Free French Forces. You were part of the volunteers-our brave companions-who maintained our country in the war with honor. You were among the first men to lead us to victory. Now that our aim has been achieved, I wish to thank you cordially and simply in the name of France. C. de Gaulle." ==Archaeological career==