On June 5, 1917, March registered for military service, a little over a month after the U.S. entered World War I. He volunteered for the U.S. Marines on July 25, and after completing his training on Parris Island was shipped to France in February 1918. Along with two other future World War I literary figures, John W. Thomason and Laurence Stallings), March embarked on USS "Von Steuben" at Philadelphia. He reached France in March 1918 and served as a sergeant in Co F, 2nd Battalion, 5th Marines, 4th Brigade of Marines, Second Division of the U.S. Army Expeditionary Force.