Faber joined the French Foreign Legion when the First World War broke out. He was assigned to the 2nd Marching Regiment of the 1st Foreign Regiment, at Bayonne on 22 August 1914. He was promoted to corporal. On 9 May 1915, the first day of the Battle of Artois at Carency near Arras he received a telegram saying his wife had given birth to a daughter. One story says that, cheering, he jumped out of the trench and was killed by a German bullet. Another, more commonly accepted, is that he was shot while carrying an injured colleague back from no-man's land during fighting between Carency and Mont-Saint-Éloi. His regiment lost 1,950 of 2,900 in their attack. Faber was posthumously awarded the Médaille militaire.