All six of Japan's first-line aircraft carriers, Akagi, Kaga, sister ships Soryu and Hiryu, and sister ships Shokaku and Zuikaku, were assigned to the mission to attack Pearl Harbor. With over 420 embarked planes, these ships constituted by far the most powerful carrier task force ever assembled. These ships were all smaller than today's Izumo class "destroyers", which are soon to be equiped with the F-35B strike fighter.