 In April 1953, the 474th Fighter-Bomber Group returned to the United States and was replaced by the 49th Fighter-Bomber Wing, also flying the F-84.During the Korean War, the large number of locations used for bases and the similarity of some geographical names prompted the Air Force to use alphanumeric identifiers for bases in addition to their proper designations.Under this system, each base in Korea received a "K number," simplifying positive identification when referring to the various bases.