battleship, large, armored warship equipped with the heaviest naval guns. The evolution of the battleship, from the ironclad warship of the mid-19th cent., received great impetus from the Civil War. By 1872 the French were building iron and steel warships, and in 1876 the British started construction of two all-steel war vessels. Developments continued to improve speed, fortification, accuracy of armament, and size. The H.M.S. Dreadnought, which was completed in 1906, was the first modern battleship and introduced the "all-big-gun" class of warship. It was armed with ten 12-in. (30.5-cm) guns and was powered by steam turbines, which developed a speed of 21 knots. The battleship became the major capital unit in modern navies, although there was only one fleet engagement of battleships in World War I and no fleet engagements in World War II. However, with the development of new aerial tactics, such as dive bombing, and the introduction (1941) of aircraft carriers as the major unit of a naval attack force, battleships became nearly obsolete. The fate of the battleship as a major weapon in modern warfare was sealed on Dec. 7, 1941, when Japanese carrier-borne aircraft attacked the U.S. navy's battleships at Pearl Harbor, sinking or badly damaging all eight. Shortly after the Korean War the last battleships of the British and American navies were decommissioned. The U.S. navy, during part of the Vietnam War, used one battleship, the New Jersey, for shore bombardment and antiaircraft defense. The four Iowa-class battleships were recommissioned in 1980s; all were again decommissioned by 1992.