 The two Shōkaku @-@ class carriers were ordered in 1937 as part of the 3rd Naval Armaments Supplement Program . No longer restricted by the provisions of the Washington Naval Treaty , which had expired in December 1936 , and with relaxed budgetary limitations , the IJN sought qualitative superiority over their foreign counterparts . Drawing on experience with their existing carriers , the Navy General Staff laid out an ambitious requirement for a ship that equaled the 96 @-@ aircraft capacity of the Akagi and Kaga , the speed of Hiryū and the defensive armament of Kaga . The new ship was also to have superior protection and range over any of the existing carriers . 
