Battlecruiser

The battlecruiser (also written as battle cruiser or battle-cruiser) was a type of capital ship of the first half of the 20th century. These were similar in displacement, armament and cost to battleships, but differed in form and balance of attributes. Battlecruisers typically had thinner armour (to a varying degree) and a somewhat lighter main gun battery than contemporary battleships, installed on a longer hull with much higher engine power in order to attain greater speeds. The first battlecruisers were designed in the United Kingdom as a successor to the armoured cruiser, at the same time as the dreadnought succeeded the pre-dreadnought battleship. The goal of the battlecruiser concept was to outrun any ship with similar armament, and chase down any ship with lesser armament; they were intended to hunt down slower, older armoured cruisers and destroy them with heavy gunfire while avoiding combat with the more powerful but slower battleships. However, as more and more battlecruisers were built, they were increasingly used alongside the better-protected battleships.

Battlecruisers served in the navies of the United Kingdom, Germany, the Ottoman Empire, Australia and Japan during World War I, most notably at the Battle of the Falkland Islands and in the several raids and skirmishes in the North Sea which culminated in a pitched fleet battle, the Battle of Jutland. British battlecruisers in particular suffered heavy losses at Jutland, where poor fire safety and ammunition handling practices left them vulnerable to catastrophic magazine explosions following hits to their main turrets from large-calibre shells. This dismal showing led to a persistent general belief that battlecruisers were too thinly armoured to function successfully. By the end of the war, capital ship design had developed, with battleships becoming faster and battlecruisers becoming more heavily armoured, blurring the distinction between a battlecruiser and a fast battleship. The Washington Naval Treaty, which limited capital ship construction from 1922 onwards, treated battleships and battlecruisers identically, and the new generation of battlecruisers planned by the United States, Great Britain and Japan were scrapped or converted into aircraft carriers under the terms of the treaty.

Improvements in armour design and propulsion created the 1930s "fast battleship" with the speed of a battlecruiser and armour of a battleship, making the battlecruiser in the traditional sense effectively an obsolete concept. Thus from the 1930s on, only the Royal Navy continued to use "battlecruiser" as a classification for the World War I–era capital ships that remained in the fleet; while Japan's battlecruisers remained in service, they had been significantly reconstructed and were re-rated as full-fledged fast battleships. Some new vessels built during that decade, the German Scharnhorst-class battleships and Deutschland-class cruisers and the French Dunkerque-class battleships are all sometimes referred to as battlecruisers, although the owning navies referred to them as "battleships" (German: Schlachtschiffe), "armoured ships" (German: Panzerschiffe) and "battleships" (French: Bâtiments de ligne) respectively.

Battlecruisers were put into action again during World War II, and only one survived to the end, Renown. There was also renewed interest in large "cruiser-killer" type warships whose design was scaled-up from a heavy cruiser rather than a lighter/faster battleship derivative, but few were ever begun and only two members of the Alaska-class were commissioned in time to see war service. Construction of large cruisers as well as fast battleships were curtailed in favor of more-needed aircraft carriers, convoy escorts, and cargo ships.

During (and after) the Cold War, the Soviet Kirov class of large guided missile cruisers have been the only ships termed "battlecruisers"; the class is also the only example of a nuclear-powered battlecruiser. As of 2024, Russia operates two units: the Pyotr Velikiy has remained in active service since its 1998 commissioning, while the Admiral Nakhimov has been inactive (in storage or refitting) since 1999.

The battlecruiser was developed by the Royal Navy in the first years of the 20th century as an evolution of the armoured cruiser. The first armoured cruisers had been built in the 1870s, as an attempt to give armour protection to ships fulfilling the typical cruiser roles of patrol, trade protection and power projection. However, the results were rarely satisfactory, as the weight of armour required for any meaningful protection usually meant that the ship became almost as slow as a battleship. As a result, navies preferred to build protected cruisers with an armoured deck protecting their engines, or simply no armour at all.

In the 1890s, new Krupp steel armour meant that it was now possible to give a cruiser side armour which would protect it against the quick-firing guns of enemy battleships and cruisers alike. In 1896–97 France and Russia, who were regarded as likely allies in the event of war, started to build large, fast armoured cruisers taking advantage of this. In the event of a war between Britain and France or Russia, or both, these cruisers threatened to cause serious difficulties for the British Empire's worldwide trade.

Britain, which had concluded in 1892 that it needed twice as many cruisers as any potential enemy to adequately protect its empire's sea lanes, responded to the perceived threat by laying down its own large armoured cruisers. Between 1899 and 1905, it completed or laid down seven classes of this type, a total of 35 ships. This building program, in turn, prompted the French and Russians to increase their own construction. The Imperial German Navy began to build large armoured cruisers for use on their overseas stations, laying down eight between 1897 and 1906. In the period 1889–1896, the Royal Navy spent £7.3 million on new large cruisers. From 1897 to 1904, it spent £26.9 million. Many armoured cruisers of the new kind were just as large and expensive as the equivalent battleship.