The Kawasaki Ki-61 Tei Hein name roughly translates into "flying swallow", but the Allies used "Tony" as its code name. Used by the Imperial Japanese Army Air Force in World War II, this single-engine, land-based tactical fighter carried the army designation "Army Type 3 Fighter". The prototype of the San-shiki-Sentohki ichi gata (Type 3 Fighter, Model 1, the official IJAAF designation) first flew in December 1941. Over 2,500 Ki-61s were produced. Its combat initiation came in 1943 around New Guinea, and missions continued throughout the war - in Southeast Asia, Okinawa, China, and as a U.S. bomber interceptor over the Japanese home islands. This was the only mass-produced Japanese WWII fighter to use a liquid-cooled inline V engine.