Protected cruiser

Protected cruisers, a type of naval cruiser of the late-19th century, gained their description because an armoured deck offered protection for vital machine-spaces from fragments caused by shells exploding above them. Protected cruisers resemble armored cruisers, which had in addition a belt of armour along the sides.
Evolution.
From the late 1850s, navies began to replace their fleets of wooden ships-of-the-line with armoured ironclad warships. However, the frigates and sloops which performed the missions of scouting, commerce raiding and trade protection remained unarmoured. For several decades, it proved difficult to design a ship which had a meaningful amount of protective armour but at the same time maintained the speed and range required of a "cruising warship". The first attempts to do so, armored cruisers like , proved unsatisfactory, generally lacking enough speed for their cruiser role.
During the 1870s the increasing power of armour-piercing shells made armouring the sides of a ship more and more difficult, as very thick, heavy armour plates were required. Even if armour dominated the design of the ship, it was likely that the next generation of shells would be able to pierce such armour. The alternative was to leave the sides of the ship vulnerable, but to armour a deck just below the waterline. Since this deck would only be struck very obliquely by shells, it could be less thick and heavy than belt armour. The ship could be designed so that the engines, boilers and magazines were under the armoured deck, and with enough displacement to keep the ship afloat and stable even in the event of damage. Cruisers with armoured decks and no side armour became known as "protected cruisers", and eclipsed the armoured cruisers in popularity in the 1880s and into the 1890s.
HMS "Shannon" was the first warship to incorporate an armoured deck; hers stretched forward from the armoured citadel to the bow. However, "Shannon" principally relied on her vertical citadel armour for protection. By the end of the 1870s ships could be found with full-length armoured decks and little or no side armour. The Italian of very fast battleships had armoured decks and guns but no side armour. The British used a full-length armoured deck in their of corvettes started in 1878; however the "Comus" class were designed for colonial service and were only capable of a speed, not fast enough for commerce protection or for fleet duties.
The breakthrough in protected-cruiser design came with the Chilean cruiser , designed and built by the British firm Armstrong at their Elswick yard. "Esmeralda" had a high speed of (dispensing entirely with sails), and an armament of two and six guns. Her protection scheme, inspired by the "Italia" class, included a full-length protected deck up to thick, and a cork-filled cofferdam along her sides. "Esmeralda" set the tone for cruiser construction for the years to come, with "Elswick cruisers" on a similar design being constructed for Italy, China, Japan, Argentina, Austria and the United States.
The French Navy adopted the protected-cruiser concept wholeheartedly in the 1880s. The "Jeune École" school of thought, which proposed a navy composed of fast cruisers for commerce raiding and torpedo boats for coastal defence, became particularly influential in France. The first French protected cruiser was , laid down in 1882, and followed by six classes of protected cruiser – and no armoured cruisers.
The Royal Navy remained equivocal about which protection scheme to use until 1887. The large , begun in 1881 and finished in 1886, were built as armoured cruisers but were often referred to as protected cruisers. While they carried an armoured belt some 10 in thick, the belt only covered of the length of the ship, and the belt was also submerged below the waterline at full load. The real protection of the class came from the armoured deck thick, and the arrangement of coal bunkers to prevent flooding. These ships were also the last armoured cruisers to be designed with sails. However, on trials it became clear that the masts and sails did more harm than good. The masts, sails and rigging were removed and replaced with a single military mast with machine-guns.
The next class of small cruisers in the Royal Navy, the , were protected cruisers, but the Royal Navy returned to the armoured cruiser with the , begun in 1885 and completed in 1889. However, in 1887 an assessment of the "Orlando" type judged them inferior to the protected cruisers and thereafter the Royal Navy only built protected cruisers, even for very large first-class cruiser designs, returning to armoured cruisers only in the late 1890s with the , laid down in 1898.
The sole major naval power to retain a preference for armoured cruisers during the 1880s was Russia. The Imperial Russian Navy laid down four armoured cruisers and one protected cruiser during the decade, all large ships with sails.
Around 1910, armour plate began to increase in quality and steam-turbine engines, lighter and more powerful than previous reciprocating engines, came into use. Existing protected cruisers became obsolete as they were slower and less well protected than new ships. Oil-fired boilers were introduced, making side bunkers of coal unnecessary but losing the protection they afforded. Protected cruisers were replaced by "light armoured cruisers" with a side armoured belt and armoured decks instead of the single deck, later developed into heavy cruisers.
Protected cruisers in service.
United States.
The first protected cruiser of the United States Navy's "New Navy" was , launched in October 1884, soon followed by in December, and a year later. A numbered series of cruisers began with "Newark" (Cruiser No. 1), although "Charleston" (Cruiser No. 2) was the first to be launched, in July 1888, and ending with another "Charleston", Cruiser No. 22, launched in 1904. The last survivor of this series is , preserved as a museum ship in Philadelphia.
The reclassification of 17 July 1920 put an end to the U.S. usage of the term "protected cruiser", the existing ships designated as plain "cruisers" with new numbers (so that the armored cruisers could retain their numbers unchanged).
Austria-Hungary.
The Austro-Hungarian Navy built and operated two classes of protected cruisers. These were two ships of the and three of the .
Britain.
The Royal Navy rated cruisers as first, second and third class between the late 1880s and 1905, and built large numbers of them for trade protection requirements. For most of this time these cruisers were built with a "protected", rather than armoured, scheme of protection for their hulls. First class protected cruisers were as large and as well-armed as armoured cruisers, and were built as an alternative to the large first class armoured cruiser from the late 1880s till 1898. Second class protected cruisers were smaller, displacing and were of value both in trade protection duties and scouting for the fleet. Third class cruisers were smaller, lacked a watertight double bottom, and were intended primarily for trade protection duties, though a few small cruisers were built for fleet scout roles or as "torpedo" cruisers during the "protected" era.
The introduction of Krupp armour in six inch thickness rendered the "armoured" protection scheme more effective for the largest first class cruisers, and no large first class protected cruisers were built after 1898. The smaller cruisers, unable to bear the weight of heavy armoured belts retained the "protected" scheme up to 1905, when the last units of the and es were completed. There was a general hiatus in British cruiser production after this time, apart from a few classes of small, fast scout cruisers for fleet duties. When the Royal Navy began building larger cruisers (less than ) again around 1910, they used a mix of armoured decks and/or armoured belts for protection, depending on class. These modern, turbine powered cruisers are properly classified as light cruisers.
France.
The French Navy built and operated a series large variety of protected cruisers classes starting with in 1882. The last ship built to this design was in 1897.
Germany.
The German Imperial Navy ("Kaiserliche Marine") built a series of protected cruisers in the 1880s and 1890s, starting with the two ships of the in the 1880s. The Navy only completed two additional classes of protected cruisers, comprising six more ships: the unique , and the five ships. The type then was superseded by the armored cruiser at the turn of the century, the first of which being . All of these ships tended to incorporate design elements from their foreign contemporaries, though the "Victoria Louise" class more closely resembled German battleships of the period, which carried lighter main guns and a greater number of secondary guns.
These ships were employed as fleet scouts and colonial cruisers. Several of the ships served with the German East Asia Squadron, and , , and took part in the Battle of Taku Forts in 1900 during the Boxer Rebellion. During a deployment to American waters in 1902, participated in the Venezuelan crisis of 1902–1903, where she bombarded Fort San Carlos. Long since obsolete by the outbreak of World War I, the five "Victoria Louise"-class vessels briefly served as training ships in the Baltic but were withdrawn by the end of 1914 for secondary duties. "Kaiserin Augusta" and the two "Irene"-class cruisers similarly served in reduced capacities for the duration of the war. All eight ships were broken up for scrap following Germany's defeat.
Italy.
The Italian "Regia Marina" (Royal Navy) ordered twenty protected cruisers between the 1880s and 1910s. The first five ships, and the , were built as "battleship destroyers", armed with a pair of large caliber guns. Subsequent cruisers were more traditional designs, and were instead intended for reconnaissance and colonial duties. Some of the ships, like and the , were designed specifically for service in Italy's colonial empire, while others, like and the , were designed as high speed fleet scouts.
Most of these ships saw action during the Italo-Turkish War of 1911–1912, where several of them supported Italian troops fighting in Libya, and another group operated in the Red Sea. There, the cruiser and two destroyers sank or destroyed seven Ottoman gunboats in the Battle of Kunfuda Bay in January 1912. Most of the earlier cruisers were obsolescent by the outbreak of World War I, and so had either been sold for scrap or reduced to subsidiary roles. The most modern vessels, including "Quarto" and the "Nino Bixio" class, saw limited action in the Adriatic Sea after Italy entered the war in 1915. The surviving vessels continued on in service through the 1920s, with some—"Quarto", , and , remaining on active duty into the late 1930s.
The Netherlands.
The Royal Netherlands Navy built several protected cruisers between 1880 and 1900. The first protected cruiser was launched in 1890 and called . It was a small cruiser with a heavy main gun; four years later a larger and more heavily armed protected cruiser was commissioned, which was called . In addition to these two cruisers, the Dutch also built six protected cruisers of the . The "Holland"-class cruisers were commissioned between 1898 and 1901, and featured, besides other armaments, two 15 cm SK L/40 single naval guns.
The Dutch protected cruisers have played a role in several international events. For example, during the Boxer Rebellion two protected cruisers ( and "Koningin Wilhelmina der Nederlanden") were sent to Shanghai to protect European citizens and defend Dutch interests.
Russia.
The Imperial Russian Navy operated a series of protected cruisers classes. The last ships built to this design where the in 1901.
Spain.
The Spanish Navy operated a series of protected cruisers classes starting with . The last ship built to this design was in 1899.
Surviving examples.
A few protected cruisers have survived as museum ships: