Musashi (武蔵), named after the former Japanese province, was one of four planned Yamato-class battleships built for the Imperial Japanese Navy (IJN), beginning in the late 1930s. The Yamato-class ships were the heaviest and most powerfully armed battleships ever constructed displacing almost 72,000 long tons (73,000 t) fully loaded and armed with nine 460-millimetre (18.1 in) main guns. Their secondary armament consisted of four 155-millimetre (6.1 in) triple-gun turrets formerly used by the Mogami-class cruisers. They were equipped with six or seven floatplanes to conduct reconnaissance.