The Shōkaku-class carriers were part of the same program that also included the Yamato-class battleships. No longer restricted by the provisions of the Washington Naval Treaty, which expired in December 1936, the Imperial Japanese Navy (IJN) was free to incorporate all those features they deemed most desirable in an aircraft carrier, namely high speed, a long radius of action, heavy protection and a large aircraft capacity. Shōkaku was laid down at Yokosuka Dockyard on 12 December 1937, launched on 1 June 1939, and commissioned on 8 August 1941.