The oldest battleships deployed by Japan during World War II were Nippon’s first dreadnought class, the four impressive Kongos (Kongo, Hiei, Haruna, and Kirishima). These were the only warships ever to have begun their service lives as battle cruisers and to be later rebuilt into battleships. They were slightly faster than contemporary RN battle cruisers, yet their protection was almost on a battleship level. Although the designs were British, Kongo was the last Japanese battleship to be actually built abroad (design and construction by Vickers of Great Britain). In a foresighted move, similar to that of the U.S. Navy with the Iowas, all four units were modernized, beginning in the mid-1930s, to increase speed specifically to serve as escorts for Japan’s projected aircraft carrier task force in the event of war. They emerged from this modernization as true battleships. (Hiei, declared in violation under the terms of the Washington Treaty, was partially disarmed, stripped of heavy side armor, and lost 25 of its 36 boilers to reduce speed; it was rearmed, rearmored, and reboilered in the 1930s.) This was a time when the IJN and the U.S. Navy considered carriers to be primarily the eyes of the fleet. The Kongos enjoyed so high a reputation that the British, during World War I, had requested them on loan!
As with the Kongos, the next Japanese battleship class, the Fusos, Japan’s first super-dreadnoughts, were completely modernized in the mid-1930s and given bizarre pagoda foremasts, in which platforms, bridges, masts, and the like seemed piled one on top of the other to no discernable pattern. Both were sunk at the Battle of Surigao Strait on 25 October 1944. The Ise class (Ise and Hyuga), follow-ons to the Fuso class, were also modernized during the 1930s.
The IJN fought its epic struggle with the United States, and to a much lesser extent with the British, almost entirely in the Pacific and lost all but one of its capital ships. In addition to Yamato and the aging Kongos, the IJN could deploy the World War I-era Fusos (Fuso and Yamashiro, laid down in 1912 and 1913, respectively); Ises (Ise and Hyuga, both laid down in 1915), and the Nagatos (Nagato and Mutsu, laid down in 1917 and 1918, respectively).