page_title: USS Alabama (BB-60)
section_title: Design
hierarchical_section_title: USS Alabama (BB-60) / Design
caption_attribution_description: English: View of the ship's forward superstructure, looking up from the port side during her shakedown period, circa December 1942. Note: Signal flags; Mk.8 fire control radar on Mk.38 main battery gun director (at top); Mk.4 fire control radar on Mk.37 secondary battery gun director at right; radio direction finder loop at left. Official U.S. Navy Photograph, now in the collections of the National Archives.
context_page_description: USS Alabama (BB-60) is a retired battleship. She was the fourth and final member of the South Dakota class of fast battleships built for the United States Navy in the 1930s. The first American battleships designed after the Washington treaty system began to break down in the mid-1930s, they took advantage of an escalator clause that allowed increasing the main battery to 16-inch guns, but Congressional refusal to authorize larger battleships kept their displacement close to the Washington limit of 35,000 long tons. A requirement to be armored against the same caliber of guns as they carried, combined with the displacement restriction, resulted in cramped ships. Overcrowding was exacerbated by wartime modifications that considerably strengthened their anti-aircraft batteries and significantly increased their crews.
  After entering service, Alabama was briefly deployed to strengthen the British Home Fleet, tasked with protecting convoys to the Soviet Union. In 1943, she was transferred to the Pacific for operations against Japan; the first of these was the Gilbert and Marshall Islands campaign that began in November that year.
context_section_description: The South Dakota class was ordered in the context of global naval rearmament during the breakdown of the Washington treaty system that had controlled battleships construction during the 1920s and early 1930s. Under the Washington and London treaties, so-called treaty battleships were limited to a standard displacement of 35,000 long tons (36,000 t) and a main battery of 14-inch (360 mm) guns. In 1936, following Japan's decision to abandon the treaty system, the United States Navy decided to invoke the "escalator clause" in the Second London treaty that allowed displacements to rise to 45,000 long tons (46,000 t) and armament to increase to 16 in (410 mm) guns. Congressional objections to increasing the size of the new ships forced the design staff to keep displacement as close to 35,000 LT as possible while incorporating the larger guns and armor sufficient to defeat guns of the same caliber.
  Alabama was 680 feet (210 m) long overall and had a beam of 108 ft 2 in (32.97 m) and a draft of 35 ft 1 in (10.69 m). She displaced 37,970 long tons (38,580 t) as designed and up to 44,519 long tons (45,233 t) at full combat load. The ship was powered by four General Electric steam turbines, each driving one propeller shaft, using steam provided by eight oil-fired Babcock & Wilcox boilers. Rated at 130,000 shaft horsepower (97,000 kW), the turbines were intended to give a top speed of 27.5 knots (50.9 km/h; 31.6 mph). The ship had a cruising range of 15,000 nautical miles (28,000 km; 17,000 mi) at a speed of 15 knots (28 km/h; 17 mph). She carried three Vought OS2U Kingfisher floatplanes for aerial reconnaissance, which were launched by a pair of aircraft catapults on her fantail. Her peace time crew numbered 1,793 officers and enlisted men, but during the war the crew swelled to 2,500.
  The ship was armed with a main battery of nine 16"/45 caliber Mark 6 guns in three triple-gun turrets on the centerline, two of which were placed in a superfiring pair forward, with the third aft. The secondary battery consisted of twenty 5-inch /38 caliber dual purpose guns mounted in twin turrets clustered amidships, five turrets on either side. As designed, the ship was equipped with an anti-aircraft battery of twelve 1.1 in (28 mm) guns and twelve .50-caliber (12.7 mm) M2 Browning machine guns, but she was completed with a battery of six quadruple 40 mm (1.6 in) Bofors guns in place of the 1.1 in guns and thirty-five 20 mm (0.79 in) Oerlikon autocannon in single mounts instead of the .50-cal. guns.
  The main armored belt was 12.2 in (310 mm) thick, while the main armored deck was up to 6 in (152 mm) thick. The main battery gun turrets had 18 in (457 mm) thick faces, and they were mounted atop barbettes that were 17.3 in (440 mm) thick. The conning tower had 16 in (406 mm) thick sides.
caption: Alabama's foremast, showing the Mk 8 radar atop the Mk 38 main battery director; note the Mk 4 radar (right) for the secondary battery
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