Shortly after his graduation from Harvard, Hays was assigned to the 88th Infantry Division, 349th Infantry Regiment, to serve as an Army chaplain during World War II. He traveled across the Atlantic Ocean in December 1943. He brought spiritual guidance and religion to soldiers on the front lines, holding regular church services and performing baptisms.
Hays kept his fellow soldiers in the holiday spirit during Easter and Christmas by holding special services. He was responsible for writing to families of fallen soldiers and those missing in action.
Hays’ infantry division, the 88th, saw combat during the latter half of the Italian campaign and was the first unit of the Fifth Army to move into Rome on June 4, 1944.
Chaplains were in high demand during the war. Hays returned to the United States in January 1946 and was honorably discharged in April 1946 as a major.