N3 Class Battleship - Background

Background

In 1916 the US had declared its intention to create a Navy "second to none"; Congress had authorized the building of a large number of battleships and battlecruisers. In response, the Japanese government also began a large programme of warship building (the 8-8 fleet). Two improved Revenge-class hulls were rebuilt into the two Renown-class battlecruisers by the Royal Navy during the war. The only new capital ships laid down during the war were the Admiral-class battlecruisers. Their design had been called into question after the Battle of Jutland in 1916 and three ships of this class were cancelled, leaving only Hood to be completed to a modified design.

The US plan had been delayed by the wartime need to build smaller vessels. Nevertheless, estimates by the Admiralty were that by the early 1920s the Royal Navy would be behind in ships. By the beginning of 1920, the Americans had completed one battleship since the end of World War I and had five more building. Seven more were intended to be laid down in 1920–21, six of these were the very large and powerful South Dakota class, armed with twelve 16-inch guns. The Japanese had finished one battleship since the end of the war and had three more under construction. To correct this state of affairs, the Admiralty initially planned to build three battleships and one battlecruiser in Fiscal Year (FY) 1921–22 and again in FY 1922–23, but this was changed to four G3-class battlecruisers to be built first, presumably to be followed by the same number of battleships the following year.

A pair of designs were prepared in June 1920, derived from the U-4 design of 1914, of ships with displacements of about 50,000 long tons (51,000 t) and armed with eight or nine guns, in four twin or three triple gun turrets mounting a new 18-inch (457 mm) gun then under development. The only limitation of the design was the inability to use British dockyards and pass through the Suez Canal. The most unusual feature of these designs was that none of the turrets were superfiring, presumably to keep the centre of gravity as low as possible and avoid the extra weight required for tall, superfiring barbettes.

The designs were revised in October and split into separate battleship and battlecruiser designs. The battleship designs were given letters of the alphabet from L through N, with the use of triple or double gun turrets shown by 3 or 2 respectively. Both 'L2' and 'L3' had superfiring guns and the armour was reduced to a 15-inch (381 mm) inclined waterline belt while the main armoured deck was 8 inches (203 mm) thick (9 inches (229 mm) where it sloped to meet the belt). They both had a designed speed of 25 knots (46 km/h; 29 mph) and had transom sterns. 'L2' displaced 52,100 long tons (52,900 t), but 'L3' was a thousand tons lighter. 'M2' and 'M3' followed in November and December and were very different from the earlier designs.

'M2' and 'M3' sacrificed fire directly astern by moving the rear turret(s) amidships in order to save weight by shortening the length of the armoured citadel. Compared to the earlier, more conventional, designs, 'M2' saved 1,540 long tons (1,560 t) and 'M3' 1,740 long tons (1,770 t). More weight was saved by reducing the designed speed to 23–23.5 knots (43–43.5 km/h; 26–27.0 mph) and using only two propeller shafts, although it was thought that this would improve manoeuvering power over four smaller propellers. These changes saved 4,350 long tons (4,420 t) for 'M2' and 5,000 long tons (5,100 t) for 'M3' over their predecessors. A lengthened version of 'M3' was chosen for further development as N3 and approved in November 1921.