Capped shells were introduced about 1900. The soft steel caps originally used were intended to flatten so as to protect the shell so that it would not shatter on impact. They were most effective below 15° striking angle, the practical limit being 20°. Later hard caps were effective over a much wider range of striking angles, corresponding to longer ranges. Also, as they were destroyed they dug a pit in the armour, damaging it and also making it less likely that the shell would either ricochet or turn away as it struck. Caps were effective against face-hardened armour, but usually reduced performance against homogeneous armour.
Unlike side armour, deck armour had to be ductile, shells and other projectiles (such as splinters and fragments) typically hitting very obliquely. The British initially used Krupp Non-Cemented (KNC) steel for their thin deck armour, but by 1915 it had been superseded by HT (High-Tensile [Strength]) steel containing a percentage of silicon. HT (or HTS) was considered superior and it was considerably less expensive.24 It was the first of a series of homogeneous armours suited to thin plates and to deck armour. After the First World War this type of armour was called NC (non-cemented). Post-1918 thicker NC armour was developed specifically to resist long-range shellfire. A 4¼in NC plate (170lbs) was expected to resist a 12in APC shell striking at a 60° angle and at 1175ft/sec, corresponding to extreme range (the corresponding standard for 5¼in plate [250lbs] was a 16in shell at 1230ft/sec). At some point the British began to refer to NCD (Non-Cemented Ductile) armour.
The British also considered coal bunkers a form of protection. In the 1880s 2ft of coal was considered equivalent to about an inch of mild steel. About a decade late DNC Sir William White resisted calls for side armour in cruisers on the grounds that a belt of coal bunkers offered better protection (he changed his mind when lightweight armours such as KC became available).
Torpedoes
Battleships as well as smaller craft were armed with torpedoes. One of Admiral Fisher’s key arguments in favour of dreadnought battleships was that their heavy guns could hit beyond the range of enemy battleship torpedoes.
By 1904 torpedo range and effectiveness were growing due to two related developments. The gyro could keep a torpedo on course beyond a few hundred yards. The heater added the energy of internal combustion to the compressed air which had previously powered torpedoes. The first RN heater torpedoes were ordered in 1907. Later the ‘wet heater’ further extended range by introducing steam into the compressed air fed into the torpedo’s engine.
A battle fleet (or squadron) in close order was an enormous target which could be hit at long range, assuming the torpedo got that far. In 1904 British battleships typically steamed 2 cables (400 yds) apart bow to bow. Battleships averaging 400ft in length would occupy a third of the length of the battle line. Attacks on such mass targets were called ‘browning’ shots, by analogy to firing at groups of troops (‘into the brown’) rather than individuals. In this case ‘browning’ shots would have a one in three chance of hitting.25 ‘Browning’ shots made long-range torpedo fire worthwhile. Torpedo attack from ahead would be particularly effective, since the battleships would run towards the torpedo and increase its effective range (the total run thus available was called the ‘virtual range’). In 1912 First Sea Lord Admiral Prince Louis Battenberg told his First Lord (Winston Churchill) that massed torpedo fire by the German battle line would likely cost the British as many as 35 per cent of their own battle line, based on the percentage of the total length of the line filled by ships
Heaters turned torpedoes into long-range ‘browning-shot’ weapons with range similar to those of heavy guns, hence attractive as capital-ship weapons. Range depended on the length of the torpedo, since that determined the volume of the air flask and also of the fuel tank. That in turn affected the design of a ship, because torpedo tubes were typically at right angles to the keel and space had to be found both to stow the torpedoes and to load them into the tubes. The experimental torpedo (17ft 10½in long) offered a range of 7500 yds at 30 knots, but if it were lengthened to 23ft it would reach 12,000 yds.26 On 7 June 1909 First Sea Lord approved a 10,800 yds (at 30 knots) setting for the new long 21in torpedo, to be carried on board battleships as well as destroyers.
UNDERWATER PROTECTION. BATTLESHIPS.
“DREADNOUGHT.”
“STVINCENT” CLASS.
“ORION” CLASS.
“KING GEORGE V.”
“IRON DUKE.”
“QUEEN ELIZABETH.”
The shift to a uniform main battery was motivated largely by the threat of torpedoes fired by enemy battleships; the object was to make it possible for British battleships to fight outside their torpedo range. That did not solve the problem of torpedoes fired by destroyers or seagoing torpedo boats, so British dreadnoughts were designed with the first underwater protection in British capital ships. This chart compares underwater protection for classes of battleships up through the Queen Elizabeths. In earlier ships it was assumed that coal would absorb some of the effect of an underwater hit, but when oil fuel was introduced it was feared that a hit might ignite it (only later did it become clear that oil fuel could help absorb the explosion).
Torpedoes were an important but largely invisible part of dreadnought armament. After Jutland, when British shells failed to prevent the German fleet from escaping, Admiral Jellicoe, who had long advocated longer-range torpedoes, saw his battleships’ torpedoes as a more important part of their armament. HMS Collingwood shows the muzzle of her stern torpedo tube in this pre-launch photograph.
DNO (Captain Reginald Bacon) pointed out that since torpedo range now matched gun range, battleships could profitably fire their torpedoes during a gun action. Although it was impractical to add more tubes, Bacon wanted more torpedoes per tube and also a heavier warhead consistent with the new range capability. Unfortunately neither that year’s battlecruiser (Indefatigable) nor its battleship (Neptune) could be rearranged for 23ft torpedoes. An additional factor was that destroyers or other torpedo craft could fire such weapons at ranges beyond those of anti-torpedo batteries. DNC proposed that the next year’s battleships be fitted for 23ft 21in torpedoes, with twelve for broadside tubes and six for stern tubes, all side-loading (as there would not be enough athwartships space to load through a breech). These weapons were first adopted in the 1909–10 programme ships: the Colossus and Orion class battleships and the Lion class battlecruisers. They had fewer submerged tubes than their predecessors (two rather than five in a battlecruiser, three in a battleship, in each case including a stern tube), partly because tubes could be reloaded faster.
Stern tubes were eliminated because of the advent of gyro angling, which was about to be introduced in 1909. Now it would be possible to fire torpedoes at 10°, 20°, 30° or 40° before or abaft the beam, rather than only dead abeam. Assistant DNO for Torpedoes (ADT) recommended that stern tubes be removed from ships with four submerged tubes. Torpedoes intended for stern tubes had required