Augustin Trébuchon was born at Montchabrier (near Le Malzieu-Ville in the Lozère) on 30 May 1878, with four younger brothers and sisters. His mother died when he was young and his father nine years later. He had been in the army since the war began in 1914. He was a communal shepherd and played accordion at village marriages before volunteering for the army on 4 August 1914. He joined the 415th Infantry Regiment as a messenger. He had already served in the second battle of the Marne and at Verdun, Artois and the Somme before arriving in the Ardennes at the end of the war. He had twice been wounded, including a severe wound to his left arm caused by an exploding artillery shell. Upon his promotion to the rank of "Soldat de Première Classe" (Private First Class) in September 1918 it was said that he was "a good soldier having always achieved his duty, of remarkable calm, setting the best example to his young comrades."