Once France entered the war, Char set literary aspirations aside in favor of political and military commitment. He first served his country in a heavy artillery regiment, and later, after the occupation by Germany and the installation of the French Vichy authority, he went underground and became an active participant in the French Resistance movement. He did not publish works during the occupation but he did continue to write. One of his major works of the wartime years was Feuillets d'Hypnos (Leaves of Hypnos), a poetic journal of the war. Written between 1941 and 1944 and published in 1946, this volume established Char as an authentic resistance writer who had, to a greater extent than many of his literary peers, risked his life to stand up to Nazi and Vichy oppression.