All I know about his service so far comes from Wikipédia.
He was mobilised in August 1914, and wounded in the head on 8 December 1914. After his recovery, he was transferred to auxiliary services in February 1916, in Caen. He worked as a cook, a stable boy, a cleaner, and a railwayman, and much else. “Everywhere he deployed the same incompetence and he determined to remain a second-class soldier for ideological reasons which he would later explain at length.” In 1918 he was a docker at Dunkirk, and learned English from the Tommies there. He was demobilised on 15 April 1919.
