Genesis and construction
The First World War saw the United States assume the mantle of one of the world’s leading naval superpowers. As an international mediator in naval re-armament, the US played a leading role in the determination of naval battle fleets post-war.
After the Five-Power Treaty was signed in Washington DC on 6 February 1922, there remained 18 ships under American flag in service, including as many as 12 new super-dreadnoughts.
During the mid 1930s US Navy planners gave serious consideration to the significance of the tactical capabilities of fast assault naval groups, and to the growing importance of air power and aircraft carriers. There was a greater emphasis placed on the need to construct new battleships, capable of attaining high speeds and combining great fire power and armor.
In the face of constantly deteriorating international relations in the mid 1930s, a decision was made to introduce small changes to the technical specifications of a battleship then on the drawing boards. In its final version the ship’s standard displacement met treaty limitations, with a hull length of 217.6 m (728 ft), a beam of 32 m and a draught of 9.8 m (approaching 38 feet). The ship’s steam turbine engines were capable of developing 115,000 SHP. The battleship was to be equipped with twelve 356mm (14”) L/50 Mk-11 guns mounted in 3 quadruple turrets. The full technical specification of the new battleships was approved on May 4, 1937 and as early as August of the same year, shipyards were contracted to start laying down the keel. The battleship, hull number BB-55, to be named the USS “North Carolina”, was to be built by the New York Navy Yard, and an identical sister vessel (BB-56), the USS “Washington”, by the Philadelphia Navy Yard.
Following Japan’s renunciation of the disarmament treaties and intelligence reports that Japan had commenced work on new, big battleships2 (their details were unknown at the time) the United States felt able to take advantage of an escalation clause. In mid-1937 a decision was made to arm the battleships with 9 new, powerful 406 mm (16”) L/45 Mk-6 guns. This tardy decision made it impossible to use the armor protection designed for the main armament3. Some armor plate sheets were already manufactured and delivered to the yards, and using new ones would not only increase the displacement to well over an estimated 35,000 ts4, but also result in delays in construction.
All in all, some small improvements to the armor system were introduced, especially in ammunition chamber areas. It had become evident that the standard displacement of 35,000ts as stated in the treaty could not be met. As a result there were attempts made to make weight reductions. Among other things, this was largely achieved through modern production technologies, including the mating of the hull plates and the assembly of mechanical elements. As a result as many as 35% of all joints were electrically welded, which, together with the lighter and more powerful than expected engines, enabled considerable weight savings of 330 ts (335 t)5. As the new, harder homogenous STS armor was used, it was possible to reduce the thickness of the hull plates from 25 mm (1”) to 19mm (3/4”) while maintaining more or less the same strength and resilience. Further weight reductions could only be achieved by reducing the main armor, an option which was obviously not retained.
As construction neared an end, actual standard displacement (BB-55) reached 37,818 ts (38,415 t), which was above the Washington Naval treaty limits6. However given the very tense international political situation at that time many politicians simply turned a blind eye to this fact. Hull number BB-55 was finally launched and named on 13 June 1940. It was sponsored by the daughter (Isabel Hoey) of the-then Governor of North Carolina,. For the next 10 months the battleship was fitted out and tested in the shipyard, to be commissioned on 9 April 1941 after a series of acceptance trials7 – one of the most powerful machines afloat in any navy.