Second South Dakota class battleships

The second South Dakota class battleships were built to produce a ship with the same characteristics as the previous North Carolina class, but with armour that was effective against 16in guns.

The aim was to produce a ship that carried the same armament of nine 16in guns in three triple turrets as the North Carolina class, had the same speed and came within the 35,000t London Naval Treaty limits, but that had an immune zone of 18,000-30,000yds against the 2,250lb 16in shell in use when the ships were designed.

USS South Dakota (BB-57) on shakedown cruise, 1942

A number of different approaches were made to achieve the required improvements without a big increase in weight. On the North Carolina class the armour was sloped at 15 degrees. This was increased to 19 degrees on the South Dakota class, allowing the maximum width of the belt armour to remain almost unchanged - only a quarter of an inch was added. The armour plate was carried some way inside the hull, creating an anti-torpedo cavity between the outer hull and the armour, saving the weight of the anti-torpedo bulges used on the North Carolina class, although this did mean that the belt had to extend down to the bottom of the ship. The deck armour was slightly thickened.

All of this effort was somewhat negated in 1939 when the Bureau of Ordnance developed a new 2,700lb 16in shell. The immune zone against this shell shrank to 20,500-26,400yds, and the immune zone on the Iowa class was also reduced. The Montana class of battleships were designed in an attempt to have a South Dakota class ship that was protected against the new shell and that was freed from treaty limits, but this class was cancelled before any had been completed.

The South Dakota was the only member of the class to be subjected to heavy shell fire, during the fighting off Guadalcanal. She was hit by twenty seven shells, with the largest being 14in. Heavy damage was sustained outside the citadel, but the main fighting parts of the ship remained undamaged. The radar, which was inevitably unarmoured, was knocked out leading to a trend to install multiple radar systems on each ship.

USS South Dakota (BB-57) under construction

The South Dakota class ships were nearly 50ft shorter than the North Carolinas, saving weight. The armoured citadel was reduced by even more, down by 75ft to 375ft. This meant that the vital parts of the ship had to be moved closer together, making the South Dakotas more cramped and uncomfortable than the North Carolinas. The reduction in size also meant that the blast from the secondary guns and the light anti-aircraft guns interfered with each other. The new ships were just as wide as the North Carolinas, and the combination of their vertical sides and fuller hull form made them both more stable and more manoeuvrable. This did mean that more power was needed from engines that had to fit into 25% less space, making the engine compartments rather cramped.

The South Dakota class ships used a tunnel stern. The two outboard propellers were enclosed in massive skegs (giant fins), with the propellers at the end of the fins. The inner propellers were mounted in the tunnel between the two skegs. This allowed for hydrodynamic refinements that increased the hull volume towards the rear of the ships and also provided anti-torpedo protection making it harder for a single torpedo hit to damage all four propellers.

All four propellers of USS Indiana (BB-58)

All four South Dakota class ships were funded as part of the Fiscal Year 1939 budget, although they were authorised in two batches. South Dakota and Indiana were authorised first. A Deficiency Appropriations Act of 25 June 1938 added funding for Massachusetts and Alabama. This came a full year before the first of the class¸ South Dakota, was actually laid down (5 July 1939). Massachusetts followed two weeks later, Indiana four months later and Alabama last in February 1940. Three of the four ships were launched before the attack on Pearl Harbor. Work on the Iowa class had already begun when the second pair of South Dakota class ships was ordered, so the Iowa was originally designated as BB59, before becoming BB61.

Three of the South Dakota class ships (South Dakota, Indiana and Massachusetts) used names repeated from the first South Dakota class, cancelled in 1922. The South Dakota differed from the other ships in the class by being fitted out to serve as a flagship, with two less 5in turrets but an extra level on the armoured conning tower.

The four members of the South Dakota class were all commissioned during 1942 - the first three in the spring and the last in August. None were built with the original anti-aircraft armament. The South Dakota was closest, and was the only one to be given the 1.1in and .50in guns, but she also carried 16 20mm guns. The other three ships were built with a mix of 40mm and 20mm guns, and had many more mounted during the war. The South Dakota ended up with seventeen quad mountings for 40mm guns and seventy seven 20mm guns!

The South Dakota BB57 served in the Pacific late in 1942 and suffered severe damage during the fighting off Guadalcanal. After undergoing repairs she served with the British Home Fleet during 1943 before returning to the Pacific where she spent the rest of the war on a mix of carrier escort and bombardment duties.

The Indiana BB58 served in the Pacific from late 1942 until the end of the war, spending most of her time on carrier escort duties, with some shore bombardment mixed in.

The Massachusetts BB59 entered service during Operation Torch, the Allied invasion of North Africa late in 1942. She then moved to the Pacific where she spent the rest of the war.

Boiler Controls, USS Alabama (BB-60)

The Alabama BB60 entered service with the British Home Fleet during 1943, a move that allowed the British to move battleships to the Mediterranean. Late in 1943 she moved to the Pacific where she spent the rest of the war.

After the war all four ships were quickly withdrawn from service. They were decommissioned by the end of 1947 and struck from the Navy List in 1961-62. Two were scrapped but Massachusetts and Alabama were preserved and are now museum ships.

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