The Shōkaku-class aircraft carriers were an improved version of the Hiryū-class ships. They had enhanced armor and AA armament, as well as a larger air group. At the time of their construction, these ships were considered the most powerful in the world. Two ships were built in the period between 1937 and 1941. Shōkaku participated in the Pearl Harbor attack, Battle of Rabaul, and Indian Ocean raids, as well as in the Battles of the Coral Sea, Eastern Solomon Islands, and Santa Cruz Islands. During the Battle in the Philippine Sea, the aircraft carrier was torpedoed by USS Cavalla and sank.