 Most Japanese forces in the theater were part of the of the Imperial Japanese Navy (IJN), which was responsible for all Japanese warships, naval aircraft, and marine infantry units.The "Rengō Kantai" was led by Admiral Isoroku Yamamoto, until he was killed in an attack by U.S. fighter planes in April 1943.Yamamoto was succeeded by Admiral Mineichi Koga (1943–44) and Admiral Soemu Toyoda (1944–45).