Built by the Imperial Japanese Navy, the Yamato-class were intended to be the largest battleships afloat. Three hulls were built, although the last, IJN Shinano, was converted to an aircraft carrier. The 71,000-ton ships IJN Yamato and IJN Musashi did have 18.1" 45-caliber guns, which fired the largest shell of any battleship, although its armor penetration was no greater than the 16" 50-caliber guns on the U.S. Iowa-class.
The class was rated at having 27-knot maximum speed. While it probably had the best optical fire control ever built, its radar was considerably inferior to that of the U.S. Iowa and South Dakota-classes.
Their speed and size were more comparable to that of the cancelled U.S. Montana class; the Iowas were optimized for speed, maneuverabilility and fire control.
The lead ship of the class was sunk by U.S. aircraft on 7 April 1945, as she led Operation TEN-GO, intended as a one-way mission, probably suicidal, formally to reinforce Japan at the Battle of Okinawa.
First to die, on 24 October 1944, the IJN Musashi was sunk by aircraft during the Battle of the Sibuyan Sea, part of the Battle of Leyte Gulf. While it had been well understood by 1944 that ships could not fully protect themselves with the antiaircraft guns of the time, Japanese defensive fire was shockingly ineffective.
As the Second World War progressed, Japan recognized the dominance of the aircraft carrier enough to order the conversion of the Yamato-class hull, IJN Shinano, from a battleship to a carrier. She was sunk on 29 November 1944 by the submarine USS Archerfish (SS-311), while being moved through the Inland Sea to a safer shipyard. A large number of civilian technicians were still on board, not all watertight compartments were implemented, and the crew was not trained in damage control.
For her size, she would have carried a small number of aircraft.