The King George V-class battleships (KGV) were the penultimate battleship design completed for the Royal Navy (RN). Five ships of the class were commissioned: King George V (1940), Prince of Wales (1941), Duke of York (1941), Howe (1942), and Anson (1942).
The Washington Naval Treaty limiting both the quantity, size (in tonnage), and armament of post World War I battleship construction had been extended by the First London Naval Treaty, but the treaty was due to expire in 1936. With increased tension between the various major naval nations, it was expected by planners that the treaty might not be renewed and the King George V-class was designed with this loss of restriction in mind.
In the event, the First London Naval Treaty of 1930 extended the 'building holiday' to 1937. Planning recommenced in 1935, drawing on previous design work. The new class would be built up to the Treaty maximum displacement of 35,000 tons. Alternatives with 16-inch, 15-inch and 14-inch main guns were considered, and it was considered that the 15-inch armament would give the best balance. Most designs were intended to make about 27 knots, and it was considered that the likely decisive range in a battle would be 12,000 to 16,000 yards. Armour and torpedo protection would form a much greater proportion of the design than previous British battleships.
In October 1935, the decision was made to use the 14-inch guns. At the time, Britain was negotiating a continuation of the Naval Treaties. The British favoured a reduction in the maximum calibre of battleship gun to 14-inch calibre, and in early October learnt that the USA would support this position if the Japanese could also be persuaded to do so. Therefore, the Admiralty decided to use a 14-inch gun on the King George V class.
The King George V class was very well-protected. The main armour belt was unusually high, stretching 23.5 ft down the side of the ship from the main deck to finish 8.5 ft below the designed waterline. Along the ship, the belt started just fore of the forward turret and finished just aft of the aft turret. The belt was at its thickest above, and at, the waterline. Over the magazines, the belt was 15 inches thick (381 mm); between the magazines, the belt was 14 inches (356 mm). The lower section of belt tapered to a thickness of between 4.5 in and 5.5 in. This armour belt was thicker than that on any other battleship built except for the much larger Yamato-class, and was deeper than that on any other battleship .
The armoured belt, together with armoured bulkhead fore and aft and the armoured main deck, formed an 'armoured citadel' protecting magazines and machinery. The bulkhead, like the main belt, was 15 in (381 mm) thick. The armoured deck was 6 in (152 mm) over the magazines and 5 in (127 mm) elsewhere.
The main gun turrets were protected by at the front and 9–12 inches (280–300 mm) on the sides. The barbettes on which they stood were 16 in thick. The conning tower was relatively light in armour at 3 inches (75 mm).
The class were also well-protected against underwater attack. The hull below the waterline was subdivided into three compartments; the outer and inner were filled with air, and the middle compartment with liquid (fuel or water). The idea was that an underwater explosion would have its force dissipated as it travelled through these compartments, and that the liquid would transmit some of the force along the ship. In case the final inner bulkhead (2 in thick) was torn, a further set of subdivided compartments would contain any leak. This scheme was designed to protect against a 1000lb warhead, and had been tested and found effective in full-scale trials.
On examination of the after her encounter with the Bismarck and the Prinz Eugen, three damaging hits were discovered, one of which, fired from Bismarck, had penetrated the torpedo protection outer bulkhead in a region very close to an auxiliary machinery space. The inner bulkhead, however, remained intact. The German shell would have actually exploded in the water if its fuse had worked properly, due to the depth which the shell had to dive before striking the Prince of Wales under her armoured belt, showing the sound design of this class of battleship's armour.
The King George V and the four other ships of the class as built carried ten guns, in two quadruple turrets fore and aft and a single twin turret behind and above the fore turret.
While some argued that this gave the battleships an inferior broadside to the eight guns of the German battleship Bismarck and her sister-ship Tirpitz, the designers of this class emphasised that the ten guns of the 14-inch class had advantages over the Bismarck's battery. They pointed out that at normal battle ranges the 14-inch gun could penetrate any practical naval armour, could shoot repeated rounds faster, and in the bad weather of the North Atlantic (hindrance to visibility and optical targeting) the extra range of bigger guns was not needed. Also, the 10 guns of the British ship could fire larger salvoes increasing hit probability. In the Battle of the Denmark Strait this theory was tested when Prince of Wales scored three hits on Bismarck while receiving seven hits from the combined fire of sixteen guns of Bismarck and Prinz Eugen after Bismarck sunk HMS Hood.
Initially the Admiralty wanted a vessel armed with nine guns in three turrets, 2 forward and 1 aft. While this was well within the capabilities of the British shipyards, the design was quickly rejected as they felt compelled to adhere to the Second London Naval Treaty signed in 1936. As a result, the class was designed to carry 12 14-inch guns in three quadruple turrets and this configuration had a heavier broadside than the nine 15-inch guns. Unfortunately it proved impossible to include this amount of firepower and the desired level of protection into a 35,000 ton displacement, plus the weight of the superimposed quadruple turret brought the stability of the vessel into question. In the end the second forward turret was changed to a smaller two gun turret in exchange for better armour protection, reducing the broadside weight to below that of the nine gun arrangement.
In service, the quad gun arrangement of two of the turrets proved to be more of an operational curse than a larger salvo blessing. Placing four 14-inch guns into a single turret made it cramped, mechanically complex and difficult to service, leading to low reliability which plagued the class throughout its career. Improved firing patterns late in the war, worked out in conjunction with the Americans, who suffered similar problems in the tight triple 14-inch turrets in the Standard battleships (especially the Tennessee-class), led to greater reliability in the quadruple turrets. Despite these issues, the King George V maintained sustained fire for the opening 30 minutes of Bismarck's final battle, and this is much longer than the average length of most battleship actions in either the First or Second World Wars. HMS Duke of York, the third of the class, fired more main armament rounds in one ship-to-ship action than any other battleship in history when she pursued the German battlecruiser Scharnhorst while in extremely heavy seas. In actual service these guns performed well.
The last naval treaty had a clause that permitted a change to 16 inch guns if another signatory did not conform to it by 1 January 1937. Although they could have invoked this clause, the effect would have been to delay construction and it was considered prudent to build with 14 inch than find themselves without the new battleships. With nearly two more years before entry into the war, the US was able to absorb a delay and built its ships with larger guns.
Four of the five King George V-class ships survived World War II; was sunk near Singapore by air attack in December 1941, a poignant foretelling of the rise of airpower over the conventional battleship. The remaining ships never suffered any serious wartime damage, except for King George V, which accidentally collided with and sank in May 1942. All of them, including the , were scrapped in 1957 and 1958.
The planned successors to the KGV class were to be the Lion-class battleships of some 40,000 tonnes with nine guns.