Editing Battlecruiser (section)

==World War I==

===Construction===
For most of the combatants, capital ship construction was very limited during the war. Germany finished the ''Derfflinger'' class and began work on the {{sclass|Mackensen|battlecruiser|4}}. The ''Mackensen''s were a development of the ''Derfflinger'' class, with 13.8-inch guns and a broadly similar armour scheme, designed for {{convert|28|kn}}.<ref>Breyer, pp. 283–84</ref>

In Britain, Jackie Fisher returned to the office of First Sea Lord in October 1914. His enthusiasm for big, fast ships was unabated, and he set designers to producing a design for a battlecruiser with 15-inch guns. Because Fisher expected the next German battlecruiser to steam at 28 knots, he required the new British design to be capable of 32 knots. He planned to reorder two {{sclass|Revenge|battleship}}s, which had been approved but not yet laid down, to a new design. Fisher finally received approval for this project on 28 December 1914 and they became the {{sclass|Renown|battlecruiser|4}}. With six [[BL 15 inch Mk I naval gun|15-inch guns]] but only 6-inch armour they were a further step forward from ''Tiger'' in firepower and speed, but returned to the level of protection of the first British battlecruisers.<ref>Roberts, pp. 46–47</ref>

At the same time, Fisher resorted to subterfuge to obtain another three fast, lightly armoured ships that could use several spare {{convert|15|in|adj=on|0}} gun turrets left over from battleship construction. These ships were essentially light battlecruisers, and Fisher occasionally referred to them as such, but officially they were classified as ''large light cruisers''. This unusual designation was required because construction of new capital ships had been placed on hold, while there were no limits on [[light cruiser]] construction. They became {{HMS|Courageous|50|2}} and her sisters {{HMS|Glorious||2}} and {{HMS|Furious|47|2}}, and there was a bizarre imbalance between their main guns of 15 inches (or {{convert|18|in|0}} in ''Furious'') and their armour, which at {{convert|3|in|spell=in}} thickness was on the scale of a light cruiser. The design was generally regarded as a failure (nicknamed in the Fleet ''Outrageous'', ''Uproarious'' and ''Spurious''), though the later conversion of the ships to [[aircraft carrier]]s was very successful.<ref>Roberts, pp. 50–52</ref> Fisher also speculated about a new mammoth, but lightly built battlecruiser, that would carry {{convert|20|in|adj=on|0}} guns, which he termed {{HMS|Incomparable}}; this never got beyond the concept stage.<ref>Breyer, p. 172</ref>

It is often held that the ''Renown'' and ''Courageous'' classes were designed for Fisher's plan to land troops (possibly Russian) on the German Baltic coast. Specifically, they were designed with a reduced [[draft (hull)|draught]], which might be important in the shallow Baltic. This is not clear-cut evidence that the ships were designed for the Baltic: it was considered that earlier ships had too much draught and not enough [[Freeboard (nautical)|freeboard]] under operational conditions. Roberts argues that the focus on the Baltic was probably unimportant at the time the ships were designed, but was inflated later, after the disastrous [[Dardanelles Campaign]].<ref>Roberts, p. 51</ref>

The final British battlecruiser design of the war was the {{sclass2|Admiral|battlecruiser|4}}, which was born from a requirement for an improved version of the ''Queen Elizabeth'' battleship. The project began at the end of 1915, after Fisher's final departure from the Admiralty. While initially envisaged as a battleship, senior sea officers felt that Britain had enough battleships, but that new battlecruisers might be required to combat German ships being built (the British overestimated German progress on the ''Mackensen'' class as well as their likely capabilities). A battlecruiser design with eight 15-inch guns, 8&nbsp;inches of armour and capable of 32 knots was decided on. The experience of battlecruisers at the [[Battle of Jutland]] meant that the design was radically revised and transformed again into a fast battleship with armour up to 12 inches thick, but still capable of {{convert|31.5|kn}}. The first ship in the class, {{HMS|Hood|51|2}}, was built according to this design to counter the possible completion of any of the Mackensen-class ship. The plans for her three sisters, on which little work had been done, were revised once more later in 1916 and in 1917 to improve protection.<ref>Roberts, pp. 55–61</ref>

The Admiral class would have been the only British ships capable of taking on the German ''Mackensen'' class; nevertheless, German shipbuilding was drastically slowed by the war, and while two ''Mackensen''s were launched, none were ever completed.<ref name=R601>Roberts, pp. 60–61</ref> The Germans also worked briefly on a further three ships, of the {{sclass|Ersatz Yorck|battlecruiser|4}}, which were modified versions of the ''Mackensen''s with 15-inch guns.<ref>Gröner, pp. 58–59</ref> Work on the three additional Admirals was suspended in March 1917 to enable more escorts and merchant ships to be built to deal with the new threat from U-boats to trade. They were finally cancelled in February 1919.<ref name=R601/>

===Battlecruisers in action===
The first combat involving battlecruisers during World War I was the [[Battle of Heligoland Bight (1914)|Battle of Heligoland Bight]] in August 1914. A force of British light cruisers and destroyers entered the [[Heligoland Bight]] (the part of the North Sea closest to [[Hamburg]]) to attack German destroyer patrols. When they met opposition from light cruisers, [[Vice Admiral]] [[David Beatty, 1st Earl Beatty|David Beatty]] took his squadron of five battlecruisers into the Bight and turned the tide of the battle, ultimately sinking three German light cruisers and killing their commander, [[Rear Admiral]] [[Leberecht Maass]].<ref>Burr, pp. 21–22</ref>
[[File:SMS Seydlitz2.jpg|thumb|{{SMS|Seydlitz||2}} was heavily damaged in the Battle of Dogger Bank]]

The German battlecruiser {{SMS|Goeben||2}} perhaps made the most impact early in the war. Stationed in the Mediterranean, she and the escorting light cruiser {{SMS|Breslau}} [[Pursuit of Goeben and Breslau|evaded British and French ships on the outbreak of war]], and steamed to Constantinople ([[Istanbul]]) with two British battlecruisers in hot pursuit. The two German ships were handed over to the [[Ottoman Navy]], and this was instrumental in bringing the [[Ottoman Empire]] into the war as one of the [[Central Powers]]. ''Goeben'' herself, renamed ''Yavuz Sultan Selim'', fought engagements against the [[Imperial Russian Navy]] in the [[Black Sea]] before being knocked out of the action for the remainder of the war after the [[Battle of Imbros]] against British forces in the [[Aegean Sea]] in January 1918.<ref>Halpern, pp. 53–58; Staff, pp. 18–20</ref>

The original battlecruiser concept proved successful in December 1914 at the [[Battle of the Falkland Islands]]. The British battlecruisers {{HMS|Inflexible|1907|2}} and {{HMS|Invincible|1907|2}} did precisely the job for which they were intended when they chased down and annihilated the German [[East Asia Squadron]], centered on the armoured cruisers {{SMS|Scharnhorst||2}} and {{SMS|Gneisenau||2}}, along with three light cruisers, commanded by Admiral [[Maximilian von Spee|Maximilian Graf Von Spee]], in the South Atlantic Ocean. Prior to the battle, the Australian battlecruiser {{HMAS|Australia|1911|2}} had unsuccessfully searched for the German ships in the Pacific.<ref>Burr, pp. 22–23</ref>
[[File:HMS Indefatigable sinking.jpg|thumb|left|''Indefatigable'' sinking during the Battle of Jutland]]

During the [[Battle of Dogger Bank (1915)|Battle of Dogger Bank]] in 1915, the aftermost barbette of the German flagship ''Seydlitz'' was struck by a British 13.5-inch shell from HMS ''Lion''. The shell did not penetrate the barbette, but it dislodged a piece of the barbette armour that allowed the flame from the shell's detonation to enter the barbette. The propellant charges being hoisted upwards were ignited, and the fireball flashed up into the turret and down into the [[magazine (artillery)|magazine]], setting fire to charges removed from their brass cartridge cases. The gun crew tried to escape into the next turret, which allowed the flash to spread into that turret as well, killing the crews of both turrets. ''Seydlitz'' was saved from near-certain destruction only by emergency flooding of her after magazines, which had been effected by [[Wilhelm Heidkamp]]. This near-disaster was due to the way that ammunition handling was arranged and was common to both German and British battleships and battlecruisers, but the lighter protection on the latter made them more vulnerable to the turret or barbette being penetrated. The Germans learned from investigating the damaged ''Seydlitz'' and instituted measures to ensure that ammunition handling minimised any possible exposure to flash.<ref>Staff, pp. 23–24, 43</ref>

Apart from the [[cordite]] handling, the battle was mostly inconclusive, though both the British flagship ''Lion'' and ''Seydlitz'' were severely damaged. ''Lion'' lost speed, causing her to fall behind the rest of the battleline, and Beatty was unable to effectively command his ships for the remainder of the engagement. A British signalling error allowed the German battlecruisers to withdraw, as most of Beatty's squadron mistakenly concentrated on the crippled armoured cruiser ''Blücher'', sinking her with great loss of life. The British blamed their failure to win a decisive victory on their poor gunnery and attempted to increase their rate of fire by stockpiling unprotected cordite charges in their ammunition hoists and barbettes.<ref>Staff, pp. 43–44; Burr, pp. 24, 33</ref>

At the [[Battle of Jutland]] on 31 May 1916, both British and German battlecruisers were employed as fleet units. The British battlecruisers became engaged with both their German counterparts, the battlecruisers, and then German battleships before the arrival of the battleships of the [[British Grand Fleet]]. The result was a disaster for the Royal Navy's battlecruiser squadrons: ''Invincible'', ''Queen Mary'', and {{HMS|Indefatigable|1909|2}} exploded with the loss of all but a handful of their crews.<ref>Halpern, pp. 318–21</ref> The exact reason why the ships' magazines detonated is not known, but the abundance of exposed cordite charges stored in their turrets, ammunition hoists and working chambers in the quest to increase their rate of fire undoubtedly contributed to their loss.<ref>Lambert 1998, pp. 54–55</ref> Beatty's flagship ''Lion'' herself was almost lost in a similar manner, save for the heroic actions of [[Major (rank)|Major]] [[Francis John William Harvey|Francis Harvey]].<ref>Roberts, p. 116</ref>

The better-armoured German battlecruisers fared better, in part due to the poor performance of British fuzes (the British shells tended to explode or break up on impact with the German armour).<ref>Halpern, p. 328</ref> {{SMS|Lützow||2}}—the only German battlecruiser lost at Jutland—had only 128 killed,<ref>Staff, pp. 41–42</ref> for instance, despite receiving more than thirty hits. The other German battlecruisers, {{SMS|Moltke||2}}, ''Von der Tann'', ''Seydlitz'', and {{SMS|Derfflinger||2}}, were all heavily damaged and required extensive repairs after the battle, ''Seydlitz'' barely making it home, for they had been the focus of British fire for much of the battle.<ref>Halpern, pp. 319–25</ref>