Armored cruiser
The armored cruiser was a type of warship of the late 19th and early 20th centuries. It was designed like other types of cruisers to operate as a long-range, independent warship, capable of defeating any ship apart from a pre-dreadnought battleship and fast enough to outrun any battleship it encountered.
For many decades, naval technology had not advanced far enough for designers to produce a cruiser that combined an armored belt with the long-range and high speed required to fulfill its mission. For this reason, beginning in the 1880s and 1890s, many navies preferred to build protected cruisers, which only relied on a lightly armored deck to protect the vital parts of the ship. However, by the late 1880s, the development of modern rapid-fire breech-loading cannons and high-explosive shells made the reintroduction of side armor a necessity. The invention of case-hardened armor in the mid-1890s offered effective protection with less weight than previously.
Varying in size, the armored cruiser was distinguished from other types of cruiser by its belt armor—thick iron plating on much of the hull to protect the ship from shellfire much like that on battleships. The first armored cruiser, the Imperial Russian Navy's, was launched in 1873 and combined sail and steam propulsion. By the 1890s, cruisers had abandoned sail and took on a modern appearance.
In 1908, the armored cruiser was supplanted by the battlecruiser, which, with armament equivalent to that of a dreadnought battleship and speed equivalent to that of a cruiser, was faster and more powerful than an armored cruiser. At around the same time there was a successor to the protected cruiser, the "light cruiser" which described small cruisers with armored belts. Although they were now considered second-rate ships, armored cruisers were still widely used in World War I due to their speed and range, and being able to outgun all but battlecruisers and battleships. Most surviving armored cruisers from this conflict were scrapped under the terms of the Washington Naval Treaty of 1922, which imposed limits on warships and defined a cruiser as a ship of 10,000 tons or less carrying guns of 8-inch caliber or less—rather smaller than many of the large armored cruisers. A handful survived in one form or another until World War II. Only one, the Greek Navy's Georgios Averof, has survived to the modern day as a museum ship.
History
Background
The armored cruiser was developed in the 1870s as an attempt to combine the virtues of the armored ironclad warship and the fast and long-ranged, but unarmored, cruisers of the time. Such a ship was desirable to protect overseas trade and, especially for the French and British, to police their vast overseas empires. The concern within higher naval circles was that without ships that could fulfill these requirements and incorporate new technology, their fleet would become obsolete and ineffective should a war at sea arise. Concern over obsolescence in official circles was further fueled by the race between the increasing size of naval guns and of armor strong enough to withstand such fire. In 1860, one of the largest naval cannons in standard use had a bore of and fired a solid shot or approximately spherical shell. By 1884, guns with as wide a bore as, firing an exploding shell, were being mounted on naval vessels. This gun could penetrate up to 34 inches of wrought iron, the earliest form of naval armor. These were muzzle-loading guns, as had been used on ships from the 1500s. Breech-loading cannon, which were readopted into naval use in the 1870s, were more destructive than muzzle loaders due to their higher rate of fire. The development of rifled cannon, which improved accuracy, and advancements in shells were other factors. Although a cruiser would not likely face the largest-caliber guns of a battleship and many navies commonly used smaller weapons as they did not wear out as fast as larger ones did, cruisers still needed some form of protection to preclude being shot to pieces.The adoption of rolled iron armor in 1865 and sandwich armor in 1870 gave ships a chance to withstand fire from larger guns. Both these protective schemes used wood as an important component, which made them extremely heavy and limited speed, the key factor in a cruiser's ability to perform its duties satisfactorily. While the first ocean-going ironclads had been launched around 1860, the "station ironclads" built for long-range colonial service such as the British and French were too slow, at 13 and 11 knots respectively, to raid enemy commerce or hunt down enemy commerce raiders, tasks usually assigned to frigates or corvettes. Powered by both sail and steam but without the additional weight of armor, these ships could reach speeds of up to 16 or 17 knots. The most powerful among them were the British, the U.S. Navy's and the French. The British especially had hoped to rely on these vessels to serve the more distant reaches of its empire. In the aftermath of the Battle of Hampton Roads in 1862, where United States wooden warships were defeated by the Confederate ironclad, the Admiralty realized that its ships could theoretically encounter an ironclad in any theater of operation.
Ship propulsion was improving but was also taking time to develop. Naval engines in the 1860s were single-expansion types, in which steam was expanded into a cylinder, pushed a piston and was released. Compounding, where steam is passed through a series of cylinders of increasing size before being released, was a more efficient process; it allowed the steam to generate more energy and use less coal to go the same distance. With greater efficiency came increasingly complex machinery and the larger potential for breakdown. However, advances in metallurgy and engineering, the potential for smaller bunkerage and the successful use of compounding in commercial engines made it an attractive option for naval engines, as well. By the 1870s, compound engines had become standard for warships. Compounding by itself did not increase power or speed significantly, although it allowed for a much greater operating range. Forced-draught systems would help increase power and speed but would not come into use until the early 1890s.
1870s: First armored cruisers
The Russian navy became the first to produce an armored warship intended for commerce raiding, with, begun in 1870 and launched in 1873, often referred to as the first armored cruiser. Armed with six and two guns, she and her sister were not fully armored but protected only by a narrow belt along the waterline. This belt, moreover, was so heavy that it sat below the ships' waterlines, which limited its benefit still further. Since they were iron-hulled, however, they were more durable than their wooden counterparts. With a top speed of only and a high coal consumption, which necessitated a full sailing rig, they were not really suited for the role of cruiser. Nevertheless, these ships were considered a new threat to British commerce in the event of war, the rationale being that any vessel, regardless of its speed, could technically be a threat to overseas commerce.The British responded with, begun in 1873, launched in 1875 and armed with two and seven rifled guns. Two ships of the followed, armed with four 10-inch and eight 9-inch guns. These early armored cruisers were essentially scaled-down versions of the first-rate ironclad warships of the time and, like their Russian counterparts, were essentially belted cruisers. Their 9-inch belts were thicker than that of the Russians but did not extend the full length of the hull due to weight but tapered off at both ends. Past this belt, the designers placed a armored deck, situated deepest in the ships, to guard magazines and machinery against plunging fire. Above this deck, space was allocated for coal bunkers and storerooms. These areas served a two-fold purpose. The bunkers served as added protection, since two feet of coal was considered the equivalent of one foot of steel. Also, if either of the ships became flooded from battle damage, it was hoped the contents of the bunkers and storerooms would aid in their continued buoyancy. Because of this unarmored protection, these ships could be considered the first protected cruisers. However, these ships also shared the liabilities of the Russian ones and because of this, the British Navy was never happy with them. Shannons top speed of and Nelsons of made them too slow to deal with fast cruisers and they were not armored well enough to take on a first-class battleship. Their armor belts also sat below the ships' waterlines, which made them of limited benefit.
The underlying problem with these early warships was that technology had not caught up to the demands being made of them; therefore, they represented a series of compromises and could not be fully effective. They were typically powered by double-expansion steam engines fed by boilers which generated steam at perhaps 60 or 70 psi pressure, which gave relatively poor efficiency and short range. Even with improved engines, the dearth of overseas refueling stations made a full sailing rig a necessity. As sailing ships required a high freeboard and a large degree of stability, the use of armored turrets as used on monitors and some battleships was ruled out, because a turret was a very heavy weight high in the ship and its placement necessitated a lower freeboard than was warranted for an oceangoing vessel. Consequently, armored cruisers retained a more traditional broadside arrangement. Their armor was distributed in a thick belt around the waterline along most of their length; the gun positions on deck were not necessarily armored at all. The limitations of these ships would not be rectified fully until decades after their construction.
Meanwhile, a battle in May 1877 between the British unarmored cruiser and the Peruvian monitor demonstrated the need for more and better-protected cruisers. Shah and the smaller wooden corvette hit Huáscar more than 50 times without causing significant damage. The Peruvian ship had an inexperienced crew unused to its cumbersome machinery, and managed to fire only six rounds, all of which missed. The engagement demonstrated the value of cruisers with armor protection.