In June 1942, during World War II, Long entered the United States Navy Reserve. He participated in the Allied invasions of Northern Africa, Sicily, Italy, and Southern France and commanded a landing craft transport (LCT) vessel in the first-wave landing at Cavalaire-sur-Mer. He was awarded four campaign medal battle stars for his service. He was discharged as a lieutenant in December 1945. In 1947, he was elected first vice commander of Louisiana's AMVETS organization.