Heavy Cruiser - 1910s: Development

1910s: Development

At the end of the 19th century, cruisers were classified as first, second or third class depending on their capabilities. First-class cruisers were typically armoured cruisers, with belt side armor, while lighter, cheaper and faster second- and third-class cruisers tended to have only an armoured deck and protective coal bunkers, rather than armoured hulls; they were hence known as protected cruisers. Their essential role had not changed since the age of sail—to serve on long-range missions, patrol for enemy warships and raid and defend commerce. Armoured cruisers had proved less versatile than needed to do this adequately. In a race to outsize and outgun one another, they had grown to around 15,000 tons and up to 9.2 and 10 inches (230 and 250 mm) in main gun caliber—very close to the pre-dreadnought battleships of the day, although they were generally ascribed to be weaker than the battleship due to their lack of armor and not appreciably faster due to the limits of engine technology at the time. While Japanese armored cruisers had distinguished themselves at the Battle of Tsushima in 1905, the armoured cruiser as it was then known had reached the end of its development. Tactics and technology were gearing towards naval encounters held over increasingly longer ranges, which demanded an armament of primarily large caliber guns. The demand for speed with which to outflank a potential enemy and fulfill its traditional role as scout for the fleet demanded a speed preferably 30 percent faster than battleships. Thirty percent was the ratio by which frigates had been faster than ships of the line in the days of sail. If a battleship sailed at 20 knots, this would mean that an armored cruiser would have to steam at least 26 or 27 knots.

Armoured cruisers could not fulfill these criteria without being built much larger and taking on a different form than they had in the past. The result was the battlecruiser. HMS Invincible and her two sister ships were designed specifically to fulfill these requirements. In a sense they were an extension of the armoured cruiser as a fast, heavily armed scout, commerce protector and cruiser-destroyer, reflected in the term originally ascribed to them, "large armored cruiser." However, they were much larger, faster and better-armed than armored cruisers, able to outpace them, stay out of range of their weapons and destroy them with relative impunity. Because they carried the heavy guns normally ascribed to battleships, they could also theoretically hold their place in a battle line more readily than armoured cruisers and serve as the "battleship-cruiser" for which Hovgaard had argued after Tsushima. All these factors made battlecruisers attractive fighting units, although Britain, Germany and Japan would be the only powers to build them. They also meant that the armored cruiser as it had been known was now outmoded. No more were built after 1910 and by the end of World War I, the majority of them had been taken out of active service.

Although Lord Fisher, the man behind the building of Invincible, had hoped to replace practically all forms of cruisers with battlecruisers, they proved to be too costly to build in large numbers. At the same time, the third class cruiser started to carry thin steel armour on the outside of its hull and became known as a light cruiser. The wide gap between the massive battlecruiser of perhaps 20,000 tons and 305 mm (12-inch) guns and the small light cruiser of up to 5,000 tons and 100 mm (4-in) or 155 mm (6-inch) guns naturally left room for an intermediate type. The first such design was the British 'Atlantic cruiser' proposal of 1912, which proposed a long-range cruiser of about 8,000 tons displacement with 190 mm (7.5-inch) guns. This was a response to a rumour that Germany was building cruisers to attack merchant shipping in the Atlantic with 170mm guns. The German raiders proved to be fictional and the 'Atlantic cruisers' were never built. However, in 1915 the requirement for long-range trade-protection cruisers resurfaced and resulted in the Hawkins class. Essentially enlarged light cruisers, the Hawkins class each carried seven 190 mm (7.5-inch) guns, and had a displacement just under 10,000 tons.

The difference between these ships and ones that would follow with the armoured cruiser were almost as pronounced as that between the armoured cruiser and the battlecruiser. One reason for this difference was the intended mission of these ships. They were not intended to serve as a junior battleship, as the armoured cruiser had been, and were not built or designed to serve in that capacity. With their main armament of 203 mm (8-inch) guns, smaller than the typical 9.2-or-10-inch (230 or 250 mm) guns of later armoured cruisers, their intended targets were other cruisers and smaller vessels. Another reason for the difference was the advances in technology and naval design, both of which the heavy cruiser was able to take advantage. Heavy cruisers, like all contemporary ships, were typically powered by oil-fired steam turbine engines and were capable of far faster speeds than armoured cruisers had ever been (propelled by coal-fired reciprocating steam engines of their era). Nonetheless, heavy cruisers often had a larger number of main guns (some armoured cruisers had a mixed instead of uniform complement of main guns), discarded the mounting of main guns in casemates in favor of center-line superfiring turrets (saved tonnage and enabled the ship to fire all guns on one broadside), and benefited from the introduction of fire control in the 1920s and 1930s, meaning that the heavy cruiser was considerably more powerful.