Picked up by the Royal Air Force in early June 1944, he commanded the London branch of the DGSS during the Battle of Normandy.

[2] He became a liaison officer with Ceux de la Libération in Paris, a 10,000-strong movement founded by three former Air Force pilots.

Every month, he brought information to Bellerive near Vichy, where Paul Badré lived with his family and communicated by radio with the Secret Intelligence Service in London.

To pass on urgent information, Masson sent messages written in invisible ink from the Austerlitz Station to an address in Vichy.

[5] On November 10, 1942, following Operation Torch, the SR Air officers flew to Algiers, leaving Captain René Gervais in charge of the network in France.

[9] In London, he chose as his drop zone the Broglie-Orbec-Bernay triangle, where he could take refuge in his mother's property on the edge of Taillefer Wood.

He recruited André Feret-Patin,[11] Emile Corouge and François Aubry, to whom he gave the mission of directing the Samson organization and establishing radio transmissions with London.

Paul Badré, who was planning the air exfiltration of General Georges at the request of Churchill's cabinet, decided to include Masson in the operation, which took place on May 20, 1943 in the Cévennes.

After a short stay in Algiers, he returned to London, where he met Colonel Passy and organized MI6 radio communications with Samson.

They were both interrogated Rue des Saussaies and Avenue Foch, where they were subjected to waterboarding, before being deported to Germany in October 1943.

In a café near the Champs-Élysées, he met René Gervais, who instructed him to integrate five SR Air posts (Brittany, Normandy, Paris, Troyes and Laon) into Samson organization.

Financially supported by Alexandre de Saint-Phalle, Samson expanded under the leadership of François Aubry and Jean Rousseau-Portalis (Billy).

[16] Put on Oscar's trail by Jean Badré, Masson set off with his men to try to free him from the Royallieu camp, but they had to give up because of the sheer number of SS guards.

[17] He was exfiltrated on the night of June 2-3 by the Royal Air Force, near Compiègne, with Jean Rousseau-Portalis and his brother Gérard Masson.