The ironclad battleship launched in 1876 had featured a heavily armored central citadel, with relatively unarmored ends; however, by the era of , battleships were armored over the length of the ship with varying zones of heavy, moderate or light armor. The U.S. Navy adopted what was formally called "all or nothing" armor in the Standard-type battleships, starting with the laid down in 1912. The Imperial Japanese Navy soon implemented the system in its "Nagato"-class battleships starting in 1917, and "All or Nothing" armor was later adopted by other navies after the First World War, beginning with the Royal Navy in its .