The F-82 was the last piston-engined fighter to be purchased in
      quantity by the USAF.  Although it appears to be two  P-51 Mustangs on
      one wing, the Twin Mustang was, except for a family resemblance ,
      an entirely new design.
      The F-82's purpose was to provide a fighter with a pilot and
      co-pilot/navigator to reduce fatigue on long-range bomber escort
      missions.  Delivery did not begin until 1946 and radar-equipped
      F-82's were used extensively as night fighters.
      Twin Mustangs based in Japan were credited with destroying the first
      three North Korean aircraft on June 27, 1950.