In 1941, he finished first on a staff course under the command of Guy Simonds, and was promoted to major in 1942, and lieutenant-colonel in January 1943. Moncel became the commanding officer of 18th Armoured Car Regiment (12th Manitoba Dragoons). Later, Moncel was posted as the General Staff Officer 1 of the II Canadian Corps, where he reorganized its general staff. Here, he was made an officer of the Order of the British Empire (OBE) and a chevalier of the Legion d'honneur (receiving the Croix de guerre with Palme in the process). In August 1944, he was promoted to Brigadier, the youngest ever Canadian to achieve that rank.