第二次ロンドン海軍軍縮会議
The Navy had been considering large battleship design schemes since 1938 to counter the threat posed by potential battleships of the Imperial Japanese Navy, which had refused to sign the Second London Naval Treaty and furthermore refused to provide details about its s. Although the Navy knew little about the "Yamato" class, some rumors regarding the new Japanese battleships placed main gun battery caliber at . The potential of naval treaty violations by the new Japanese battleships resulted in the remaining treaty powers, Britain, France and the United States, invoking the tonnage "Escalator Clause" of the Second London Naval Treaty in June 1938, which raised the maximum standard displacement limit from to .