In February 1942, Cabell was assigned as assistant executive for technical planning and coordination in the Office of the Chief of the Air Corps, and promoted to Colonel. During the summer of 1943, he attended the first course of the Army and Navy Staff College. In late 1943, he was transferred to the Eighth Air Force and assumed command of the 45th Combat Bombardment Wing. In April 1944, he became director of plans for the U.S. Strategic Air Force in Europe, and later that year, having achieved the rank of brigadier general, became director of operations and intelligence for the Mediterranean Air Forces. During the war he served both at air force headquarters at the Pentagon and in the European Theater.