In mid-1915 he served as commander of the French Expeditionary Corps that was committed to the Dardanelles campaign. He was wounded on 30 June, and subsequently lost his right arm. From December 1915 to December 1916 and from June 1917 until the end of the war he commanded the Fourth Army on the Western Front, where he gained distinction for his use of elastic defense during the Second Battle of the Marne. On 22 November 1918, he entered the city of Strasbourg, overthrowing the Soviet government that had been proclaimed there on 11 November 1918.