The United States entered World War I in April 1917, and Ward's regiment soon became part of the 3rd Infantry Division. He served on the Western Front with the American Expeditionary Force (AEF) during the war. During the Second Battle of the Marne, in July 1918, under conditions that rendered other officers in charge useless, he took charge of the 2nd Battalion, 10th Field Artillery Regiment and kept the battalion effective until the tide of Germans was turned back. He was later awarded the Silver Star Citation for his actions. He continued to serve on the Western Front until the war ended with the Armistice with Germany on November 11, 1918.