US Navy: South Dakota-class (BB-49 to BB-54)

South Dakota-class (BB-49 to BB-54) - Specifications 

• Displacement: 43,200 tons
• Length: 684 ft.
• Beam: 105 ft.
• Draft: 33 ft.
• Propulsion: Turbo-electric transmission turning 4 propellers
• Speed: 23 knots

Armament (as built)

• 12 × 16 in. gun (4 × 3)
• 16 × 6 in. guns
• 4 × 3 in. guns
• 2 × 21 in. torpedo tubes

South Dakota-class (BB-49 to BB-54) - Background:

Authorized on March 4, 1917, the South Dakota-class represented the final set of battleships called for under the Naval Act of 1916.  Comprising six vessels, the design in some ways marked a departure from the Standard-type specifications that had been utilized in the preceding Nevada, Pennsylvania, New Mexico, Tennessee, and Colorado classes.  This concept had called for vessels that had similar tactical and operational traits such as a minimum top speed of 21 knots and turn radius of 700 yards.  In creating the new design, naval architects sought to utilize lessons learned by Royal Navy and Kaiserliche Marine during the early years of World War I.  Construction was then delayed so that information gleaned during the Battle of Jutland could be incorporated into the new vessels.  

South Dakota-class (BB-49 to BB-54) - Design:

An evolution of the Tennessee- and Colorado classes, the South Dakota-class employed similar bridge and lattice mast systems as well as turbo-electric propulsion.  The latter powered four propellers and would give the ships a top speed of 23 knots.  This was faster than its predecessors and showed the US Navy's understanding that British and Japanese battleships were increasing in speed.  Also, the new class varied in that it trunked the ships' funnels into a single structure.  Possessing a comprehensive armor scheme that was approximately 50% stronger than that created for HMS Hood, the South Dakota's main armor belt measured a consistent 13.5" while protection for the turrets ranged from 5" to 18" and the conning tower 8" to 16".  

Continuing a trend in American battleship design, the South Dakotas were intended to mount the main battery of twelve 16" guns in four triple turrets.  This marked an increase of four over the earlier Colorado-class.  These weapons were capable of an elevation of 46 degrees and possessed a range of 44,600 yards.  In a further departure from the Standard-type ships, the secondary battery was to consist of sixteen 6" guns rather than the 5" guns used on early battleships.  While twelve of these guns were to be placed in casemates, the remainder was located in open positions around the superstructure.    

South Dakota-class (BB-49 to BB-54) - Ships & Yards:

• USS South Dakota (BB-49) - New York Naval Shipyard
• USS Indiana (BB-50) - New York Naval Shipyard
• USS Montana (BB-51) - Mare Island Naval Shipyard
• USS North Carolina (BB-52) - Norfolk Naval Shipyard
• USS Iowa (BB-53) - Newport News Shipbuilding Corporation
• USS Massachusetts (BB-54) - Fore River Shipbuilding

South Dakota-class (BB-49 to BB-54) - Construction:

Though the South Dakota-class was approved and the design completed prior to the end of World War I, construction continued to be delayed due to the US Navy's need for destroyers and escort vessels to combat German U-boats.  With the end of the conflict, work commenced with all six vessels being laid down between March 1920 and April 1921. During this time, concern arose that a new naval arms race, similar to the one that had preceded World War I, was about to begin.  In an effort to avoid this, President Warren G. Harding held the Washington Naval Conference in late 1921, with the object of placing limits on warship construction and tonnage. Beginning on November 12, 1921, under the auspices of the League of Nations, the representatives gathered at Memorial Continental Hall in Washington DC. Attended by nine countries, the key players included the United States, Great Britain, Japan, France, and Italy.  Following exhaustive negotiations, these countries agreed on a 5:5:3:1:1 tonnage ratio as well as limits on ship designs and overall caps on tonnage.   

Among the restrictions imposed by the Washington Naval Treaty was that no vessel could exceed 35,000 tons.  As the South Dakota-class rated 43,200 tons, the new vessels would be in violation of the treaty.  In order to comply with the new restrictions, the US Navy ordered the construction of all six ships to halt on February 8, 1922, two days after the treaty's signing.  Of the vessels, work on South Dakota had progressed the furthest at 38.5% complete.  Given the size of the ships, no conversion approach, such as completing the battlecruisers Lexington (CV-2) and Saratoga (CV-3) as aircraft carriers, was available.  As a result, all six hulls were sold for scrap in 1923.  The treaty effectively halted American battleship construction for fifteen years and the next new vessel, USS North Carolina (BB-55), would not be laid down until 1937.

Selected Sources:

• NHHC: South Dakota-class
• Global Security: South Dakota-class
• MaritimeQuest: South Dakota-class