South Dakota-class battleship (1939)

The South Dakota-class battleships were a group of four fast battleships built for the United States Navy in the late 1930s and early 1940s. These ships—South Dakota (BB-57), Indiana (BB-58), Massachusetts (BB-59), and Alabama (BB-60)—were designed under the limitations of the Second London Naval Treaty, which restricted displacement to 35,000 long tons.

The class represented a significant advancement in battleship design, achieving a remarkable combination of firepower, protection, and speed within the treaty constraints. They were armed with nine 16-inch (406 mm)/45 caliber Mark 6 guns in three triple turrets, and possessed a heavy secondary battery of sixteen 5-inch (127 mm)/38 caliber dual-purpose guns for anti-aircraft and surface defense.

The South Dakota class incorporated an effective "all-or-nothing" armor scheme, concentrating heavy protection around the vital areas of the ship, such as the magazines and machinery spaces. This made them among the most heavily protected battleships of World War II.

Their powerful machinery plant allowed them to achieve speeds of up to 27.5 knots (50.9 km/h; 31.6 mph), enabling them to operate effectively alongside aircraft carriers.

All four ships saw extensive service in the Pacific Theater of World War II, participating in major battles such as the Guadalcanal Campaign, the Battle of the Philippine Sea, and the Battle of Okinawa. They played crucial roles in providing naval gunfire support for amphibious landings and in defending carrier task forces from air attack. The South Dakota-class battleships proved to be highly successful designs, contributing significantly to the Allied victory. After the war, they were decommissioned and eventually scrapped, with Massachusetts preserved as a museum ship.