Editing Battlecruiser (section)

==Interwar period==
In the years immediately after World War I, Britain, Japan and the US all began design work on a new generation of ever more powerful battleships and battlecruisers. The new burst of shipbuilding that each nation's navy desired was politically controversial and potentially economically crippling. This nascent arms race was prevented by the [[Washington Naval Treaty]] of 1922, where the major naval powers agreed to limits on capital ship numbers.<ref>Breyer, pp. 62–64, 70–72</ref> The German navy was not represented at the talks; under the terms of the [[Treaty of Versailles]], Germany was not allowed any modern capital ships at all.<ref>Chesneau, p. 218</ref>

Through the 1920s and 1930s only Britain and Japan retained battlecruisers, often modified and rebuilt from their original designs. The line between the battlecruiser and the modern fast battleship became blurred; indeed, the Japanese ''Kongō''s were formally redesignated as battleships after their very comprehensive reconstruction in the 1930s.<ref name=j5>Jentschura, Jung & Mickel, p. 35</ref>

===Plans in the aftermath of World War I===

''Hood'', launched in 1918, was the last World War I battlecruiser to be completed. Owing to lessons from Jutland, the ship was modified during construction; the thickness of her belt armour was increased by an average of 50 percent and extended substantially, she was given heavier deck armour, and the protection of her magazines was improved to guard against the ignition of ammunition. This was hoped to be capable of resisting her own weapons—the classic measure of a "balanced" battleship. ''Hood'' was the largest ship in the Royal Navy when completed; because of her great displacement, in theory she combined the firepower and armour of a battleship with the speed of a battlecruiser, causing some to refer to her as a fast battleship. However, her protection was markedly less than that of the British battleships built immediately after World War I, the {{sclass|Nelson|battleship|4}}.<ref name="Breyer, p. 168"/>

[[File:Lexington class battlecruiser2.jpg|thumb|left|''Lexington''-class battlecruiser (painting, c. 1919)]]
The navies of Japan and the United States, not being affected immediately by the war, had time to develop new heavy {{convert|16|in|mm|adj=on}} guns for their latest designs and to refine their battlecruiser designs in light of combat experience in Europe. The Imperial Japanese Navy began four {{sclass|Amagi|battlecruiser|2}}s. These vessels would have been of unprecedented size and power, as fast and well armoured as ''Hood'' whilst carrying a main battery of ten 16-inch guns, the most powerful armament ever proposed for a battlecruiser. They were, for all intents and purposes, fast battleships—the only differences between them and the {{sclass|Tosa|battleship|2}}s which were to precede them were {{convert|1|in|mm|adj=off}} less side armour and a {{convert|.25|kn}} increase in speed.<ref>Breyer, p. 353</ref> The United States Navy, which had worked on its battlecruiser designs since 1913 and watched the latest developments in this class with great care, responded with the {{sclass|Lexington|battlecruiser|4}}. If completed as planned, they would have been exceptionally fast and well armed with eight 16-inch guns, but carried armour little better than the ''Invincible''s—this after an {{convert|8000|LT|t|adj=on}} increase in protection following Jutland.<ref>Breyer, p. 234</ref> The final stage in the post-war battlecruiser race came with the British response to the ''Amagi'' and ''Lexington'' types: four {{convert|48000|LT|t|adj=on}} [[G3 battlecruiser]]s. Royal Navy documents of the period often described any battleship with a speed of over about {{convert|24|kn}} as a battlecruiser, regardless of the amount of protective armour, although the G3 was considered by most to be a well-balanced fast battleship.<ref>Gardiner & Gray, pp. 41–42</ref>

The Washington Naval Treaty meant that none of these designs came to fruition. Ships that had been started were either broken up on the [[slipway]] or converted to aircraft carriers. In Japan, ''Amagi'' and {{ship|Japanese aircraft carrier|Akagi||2}} were selected for conversion. ''Amagi'' was damaged beyond repair by the [[1923 Great Kantō earthquake]] and was broken up for [[ship breaking|scrap]]; the hull of one of the proposed ''Tosa''-class battleships, {{ship|Japanese aircraft carrier|Kaga||2}}, was converted in her stead.<ref>Gardiner & Gray, p. 235</ref> The United States Navy also converted two battlecruiser hulls into aircraft carriers in the wake of the Washington Treaty: {{USS|Lexington|CV-2|6}} and {{USS|Saratoga|CV-3|6}}, although this was only considered marginally preferable to scrapping the hulls outright (the remaining four: ''Constellation'', ''Ranger'', ''Constitution'' and ''United States'' were scrapped).<ref>Gardiner & Gray, p. 119</ref> In Britain, Fisher's "large light cruisers," were converted to carriers. ''Furious'' had already been partially converted during the war and ''Glorious'' and ''Courageous'' were similarly converted.<ref>Gardiner & Gray, p. 40</ref>

===Rebuilding programmes===
[[File:HMS Repulse (1919) profile drawing.png|thumb|left|350px|''Repulse'' as she was in 1919]]
[[File:HMS Renown (1939) profile drawing.png|thumb|left|350px|''Renown'', as reconstructed, in 1939]]

In total, nine battlecruisers survived the Washington Naval Treaty, although HMS ''Tiger'' later became a victim of the [[London Naval Conference 1930]] and was scrapped.<ref>Burt, p. 48</ref> Because their high speed made them valuable surface units in spite of their weaknesses, most of these ships were significantly updated before World War II. {{HMS|Renown|1916|2}} and {{HMS|Repulse|1916|2}} were modernized significantly in the 1920s and 1930s. Between 1934 and 1936, ''Repulse'' was partially modernized and had her [[bridge (nautical)|bridge]] modified, an aircraft [[hangar]], [[aircraft catapult|catapult]] and new gunnery equipment added and her anti-aircraft armament increased. ''Renown'' underwent a more thorough reconstruction between 1937 and 1939. Her deck armour was increased, new turbines and boilers were fitted, an aircraft hangar and catapult added and she was completely rearmed aside from the main guns which had their elevation increased to +30 degrees. The bridge structure was also removed and a large bridge similar to that used in the {{sclass|King George V|battleship (1939)|0}} battleships installed in its place. While conversions of this kind generally added weight to the vessel, ''Renown''{{'}}s tonnage actually decreased due to a substantially lighter power plant. Similar thorough rebuildings planned for ''Repulse'' and ''Hood'' were cancelled due to the advent of [[World War II]].<ref>Breyer, pp. 157–58, 172</ref>

Unable to build new ships, the Imperial Japanese Navy also chose to improve its existing battlecruisers of the ''Kongō'' class (initially the {{ship|Japanese battleship|Haruna||2}}, {{ship|Japanese battleship|Kirishima||2}}, and {{ship|Japanese battleship|Kongō||2}}—the {{ship|Japanese battleship|Hiei||2}} only later as it had been disarmed under the terms of the Washington treaty) in two substantial reconstructions (one for ''Hiei''). During the first of these, elevation of their main guns was increased to +40 degrees, [[anti-torpedo bulges]] and {{convert|3800|LT|t}} of horizontal armour added, and a "pagoda" mast with additional command positions built up. This reduced the ships' speed to {{convert|25.9|kn}}. The second reconstruction focused on speed as they had been selected as fast escorts for aircraft carrier task forces. Completely new main engines, a reduced number of boilers and an increase in hull length by {{convert|26|ft|m|1}} allowed them to reach up to 30 knots once again. They were reclassified as "fast battleships," although their armour and guns still fell short compared to surviving World War I–era battleships in the American or the British navies, with dire consequences during the [[Pacific War]], when ''Hiei'' and ''Kirishima'' were easily crippled by US gunfire during actions off Guadalcanal, forcing their scuttling shortly afterwards.<ref>Breyer, pp. 339–40</ref> Perhaps most tellingly, ''Hiei'' was crippled by medium-caliber gunfire from heavy and light cruisers in a close-range night engagement.<ref>Stille, pp. 19–20</ref>

There were two exceptions: Turkey's ''Yavuz Sultan Selim'' and the Royal Navy's ''Hood''. The Turkish Navy made only minor improvements to the ship in the interwar period, which primarily focused on repairing wartime damage and the installation of new fire control systems and anti-aircraft batteries.<ref>Chesneau, p. 406</ref> ''Hood'' was in constant service with the fleet and could not be withdrawn for an extended reconstruction. She received minor improvements over the course of the 1930s, including modern fire control systems, increased numbers of anti-aircraft guns, and in March 1941, radar.<ref>Konstam, pp. 33–34</ref>

===Naval rearmament===
In the late 1930s navies began to build capital ships again, and during this period a number of large commerce raiders and small, fast battleships were built that are sometimes referred to as battlecruisers, such as the {{sclass|Scharnhorst|battleship|1}}s and {{sclass|Deutschland|cruiser|1}}s and the French {{sclass|Dunkerque|battleship|1}}s.{{refn|The German {{sclass|Scharnhorst|battleship|1}}s and {{sclass|Deutschland|cruiser|1}}s and the French {{sclass|Dunkerque|battleship|1}}s are all sometimes referred to as battlecruisers, although the owning navies referred to them as "battleships" ({{langx|de|Schlachtschiffe}}), "armoured ships" ({{langx|de|Panzerschiffe}}) and "battleships" ({{langx|fr|Bâtiments de ligne}}) respectively. Since neither their operators nor a significant number of naval historians classify them as such, they are not discussed in this article.<ref>Gröner, pp. 31, 60; Gille, p. 139; Koop & Schmolke, p. 4</ref><ref name="Gardiner & Chesneau, p. 259">Chesneau, p. 259</ref><ref>Bidlingmaier, pp. 73–74</ref>|group=Note}} Germany and Russia designed new battlecruisers during this period, though only the latter laid down two of the 35,000-ton {{sclass|Kronshtadt|battlecruiser|4}}. They were still on the slipways when the Germans invaded in 1941 and construction was suspended. Both ships were scrapped after the war.<ref>McLaughlin 2004, pp. 112, 114</ref> The Germans planned three battlecruisers of the {{sclass2|O|battlecruiser|4}} as part of the expansion of the [[Kriegsmarine]] ([[Plan Z]]). With six 15-inch guns, high speed, excellent range, but very thin armour, they were intended as commerce raiders. Only one was ordered shortly before World War II; no work was ever done on it. No names were assigned, and they were known by their contract names: 'O', 'P', and 'Q'. The new class was not universally welcomed in the Kriegsmarine. Their abnormally-light protection gained it the derogatory nickname ''Ohne Panzer Quatsch'' (without armour nonsense) within certain circles of the Navy.<ref>Garzke & Dulin, pp. 353–54, 363; Gröner, p. 68</ref>