In 1940 Foote joined the Mississippi National Guard and was commissioned as captain of artillery. After being transferred from one stateside base to another, his battalion was deployed to Northern Ireland in 1943. The following year, Foote was charged with falsifying a government document relating to the check-in of a motor pool vehicle he had borrowed to visit a girlfriend in Belfast, Teresa Lavery—later his first wife—who lived two miles beyond the official military limits. He was court-martialed and dismissed from the army. Shelby and Teresa divorced while she was living with his mother in New Orleans, after Shelby sent her to the U.S. on a warship convoy.