Hoover began his Army career as an infantry private in the Illinois National Guard. His infantry regiment, however, was quickly converted into the 123rd Field Artillery regiment. Hoover received numerous promotions and eventually became a non-commissioned sergeant. He fought in the battles of Saint-Mihiel and Meuse-Argonne. After the war he served in Luxembourg, with the American Army of Occupation in Germany. Of his military service he said, "My army experience cured me of being a socialist."