Joseph D. Reilly was born and raised in Janesville, Wisconsin and worked in a factory in Delavan, Wisconsin before enlisting in the Army in 1943. Near the end of his basic training, Reilly signed up for jump school to become a paratrooper. His first jump in battle was the D-Day invasion of Normandy, France. Reilly also fought to defend the town of Bastonge during the Battle of the Bulge. He was awarded the Bronze Star for his part in that battle. In March 1945 Reilly married Eileen Campbell of Darwen Lancashire, England. They had met while he was on furlough in 1943 and kept in touch before deciding to get married. They eventually moved back to Janesville in 1946.