An American soldier poses in a gas mask outside his tent at a U.S. Army training camp, circa 1917-1918. Gas mask drills became standard practice for recruits preparing for deployment to the Western Front, where chemical weapons had introduced a new and feared dimension to trench warfare. The soldier's relaxed stance suggests this was a posed photograph rather than an active drill, offering a glimpse of camp life during American mobilization for the First World War. Project: 218653