After World War I ended, Duval participated in the Allied intervention in the Russian Civil War, serving in Siberia with the mission of General Maurice Janin until 20 June 1920. He served in Syria in 1921, then joined the 27th "Chasseurs Alpins" Battalion in Annecy in 1922. He studied at the "École supérieure de guerre" (French war college) from 1924 to 1926, then was assigned in 1926 to the staff of the 19th Army Corps in Algiers, his first assignment in Algeria. He married on 1 June 1927. He was promoted to "commandant" on 25 December 1932. Transferred to Fez in French Morocco, he participated in the High Atlas campaign at the end of the pacification of Morocco. From 1933 to 1935, he was deputy head of the resident general's cabinet in French Morocco. From 1935 to 1939, he was on the general staff and supreme commander of troops in French Morocco.