The class was a pair of armored cruisers built for the German (Imperial Navy) under the terms of the First Naval Law, which initiated a major naval expansion program. Two ships of the class were built, and , between 1900 and 1904. Their design was heavily based on Germany's previous armored cruiser, , with a series of incremental improvements. These included a revised armor layout to improve internal protection, along with an upgraded main battery armament that consisted of four guns instead of the two carried by . The new ships also received more powerful propulsion systems, making them slightly faster. spent her peacetime career as a gunnery-training ship while initially served as the flagship of the 's (Home Fleet) reconnaissance forces. By 1909, she had been replaced by more modern cruisers and joined as a training vessel.
Following the outbreak of World War I in July 1914, both vessels were mobilized; was assigned to the cruiser division in the Baltic Sea and was sunk by Russian naval mines off Memel in November, though most of her crew was safely taken off. initially served in the North Sea, supporting the raid on Yarmouth in November 1914 before transferring to the Baltic to replace her lost sister. had little better luck, being torpedoed by British submarines twice in 1915, the first, in July, caused serious damage and necessitated lengthy repairs. The second, in October, caused an internal magazine explosion that destroyed the ship and killed 672; only 3 sailors survived. The sinking was the greatest single loss of life for the German fleet in the Baltic during the war.
Background
The First Naval Law in Germany, passed on 1 April 1898, projected a force of twelve armored cruisers to be employed on overseas duties in the German colonies or in home waters for operations with the main battle fleet. Of these, six were to serve with the main battle fleet, three were to be stationed in the German colonial empire, and the other three would remain in reserve. By 1898, the German navy possessed ten vessels it counted in the armored cruiser category, which meant that two more vessels needed to be built to comply with the Naval Law's requirements. But in addition to the fixed numerical requirement, the Naval Law also mandated that a ship would be considered obsolete once it reached 20 years of age, and three of the existing cruisers were well overage. Thus, the navy needed to build five new cruisers as soon as possible to meet the requirements laid out in the law.
The first vessel to be ordered under the provisions of the Naval Law became the armored cruiser ; the ship was ordered under the provisional designation "A". This ship was an alteration of the design of an earlier vessel, , equipped with fewer guns and thinner but more comprehensive armor in a trade-off for higher speed and lower cost. These reductions were necessary from a financial perspective, given the scale of the German naval armament program. But they left many unanswered questions, particularly over the armament and speed of future ships, as compromise solutions had to have been adopted for to meet the strict financial limitations. The ship nevertheless became the basis for the armored cruisers that would be built in Germany to fill the fleet screening role.
According to the law, one large cruiser was to be built per year until the full complement of twelve vessels were in service, so design work began immediately on a follow-on vessel to fulfill the requirement. In practice, however, construction of the next cruiser—designated "B" until a name was formally chosen—was deferred by one year, owing to the need to build a total of seven new battleships by 1900. The deferment allowed more time for the designers to improve upon the basic template and attempt to resolve the deficiencies in armament and speed.
Design
Discussions over the main open questions—speed and armament—resumed in early 1899 and included a paper submitted by (KAdm—Rear Admiral) Max von Fischel, the head of the military section of the (RMA—Imperial Naval Office). He argued that speed was the utmost priority and should be increased over that of . If the weight of the new armament allowed it, he also stated that the two single guns mounted in the earlier cruiser be replaced by four guns in twin-gun turrets. The basis of his argument lay in the fact that the new cruiser was most likely to engage other enemy armored cruisers, not battleships, and that contemporary foreign cruisers carried armor no thicker than , and the smaller gun was more than capable of penetrating such armor at normal battle ranges. The smaller gun also had a higher rate of fire, and doubling the number of barrels improved fire direction. Fischel also proposed raising the armor deck to increase reserve buoyancy in the case of flooding through shell holes above the waterline.
Fischel's paper passed to KAdm Wilhelm Büchsel, the head of the RMA's technical department, to be developed in greater detail, with particular emphasis on what weight savings would be required in other aspects to meet Fischel's proposal for the armament. The layout of the propulsion system was considered, specifically whether it would be possible to revert from a three-propeller arrangement back to two screws, but the designers concluded that it would be impossible to fit engines large enough to meet the speed requirements given the space allowed. Büchsel's report was discussed on 9 June in a meeting of senior RMA personnel, including Admiral Alfred von Tirpitz, the head of the RMA. Tirpitz objected to the stated top speed of the new cruiser, which was set to be , since this did not meet his requirement that the ship must be at least three knots faster than the latest battleships. He therefore requested that the design department try to increase speed by half a knot. The officers agreed that the change in armament was acceptable as proposed, but they noted that it amounted to an increase in cost that was best left undisclosed for the time being, owing to financial difficulties with other construction projects.
Tirpitz then presented the proposal to Kaiser Wilhelm II for his approval, noting the planned improvements over . In addition to the new main battery, the citadel armor would be extended to cover the sides of the main turret substructures, and a heavy military mast would be fitted. These improvements would come at the cost of shortening the casemate for the secondary guns and reducing the standard coal storage, along with accepting a slight increase in displacement. The basic hull size and shape remained largely identical, as did the ships' secondary battery. By this time, the speed issue remained unresolved, as the designers grappled with the problems of providing enough power from the boilers and fitting the engines into the space provided, since the dimensions of the new ship could not be increased. These struggles continued for some time, as the speed calculations indicated that the necessary power would require an increased displacement, which in turn mandated greater buoyancy from the hull structure, which reduced the hydrodynamic efficiency of the hull shape (and thus negated any increase in speed). Eventually, the designers were able to fit a propulsion system rated to produce , slightly less than the that was predicted to be necessary, though it was hoped this would be sufficient.
Wilhelm II approved the proposed design on 9 October, but further detailed work continued for some time. The designers eventually came to the conclusion that the desired power output was unattainable, given the constraints on the ship's size and hull shape, and so they settled for the 16,200 PS output with the hope that future developments might allow the boilers to be run at greater power. The 1900/01 naval budget was approved on 5 April 1900, allowing the contract for the first member of the class to be placed. Nearly a year later, on 16 March 1901, Captain Rudolf von Eickstedt informed Tirpitz that recent model tests suggested that the ship would require as much as to reach her intended top speed. By that time, the second ship of the class, ordered as , had begun construction as well. It was determined that coverings for the ships' propeller shafts would provide an increase in hydrodynamic efficiency equivalent to about , though "B" was too far advanced in construction to allow them to be installed.
General characteristics
The ships of the class were long at the waterline and overall, and had a beam of . The ships were designed to displace , but at full load displaced up to ; they had a draft of forward and aft. The ships' hulls were constructed from transverse and longitudinal steel frames, over which the steel hull plates were riveted. The vessels contained fourteen watertight compartments and a double bottom that extended for 60 percent of the length of the hull. Their superstructure consisted of a primary conning tower forward with a bridge structure and a larger structure further aft that had a small, secondary conning tower atop it. The designers reverted to the use of two heavy military masts that had been discarded in s design.
The Germans regarded the vessels as good sea boats, with gentle motion when the ships' lower fuel bunkers were full. The ships were responsive to commands from the helm, and steering was controlled with a single rudder. They lost up to 60 percent speed with the rudder hard over. While steaming in heavy seas, they suffered only minimal speed loss. The ships had a standard crew of 35 officers and 551 enlisted men, though when serving as a squadron flagship this could be augmented by another 9 officers and 44 enlisted men. The ships were equipped with several boats, including a pair of picket boats, a launch, a pinnace, two cutters, two yawls, and two dinghies.
and were powered by three vertical 3-cylinder triple-expansion engines; the center shaft drove a three-bladed screw in diameter, while the two outboard shafts powered four-bladed screws in diameter. The engines were supplied with steam by fourteen coal-fired Dürr boilers, a type of water-tube boiler produced by , which were ducted into three funnels. Compared to those on earlier German cruisers, the propeller shafts for were shortened and better faired into the hull lines to reduce the amount of drag they induced, and they were made self-supporting; these changes were incorporated into all future cruisers and battleships built by the .
The propulsion system was rated at for Prinz Adalbert and for Friedrich Carl and top speeds of and , respectively. Both ships reached higher horsepower figures on trials, though their speeds were not significantly improved. The ships were designed to carry of coal, though storage could be increased to . This enabled a maximum range of up to at a cruising speed of . Electrical power was supplied by four generators with a total output of at 110 volts.
Armament
and were armed with a main battery of four SK L/40 guns in two twin turrets, one on either end of the main superstructure fore and aft. The four guns were supplied with a total of 340 rounds of ammunition, or 85 shells per gun. The shells were a mixture of armor-piercing, high-explosive, and solid steel rounds. The C/04 turrets could depress to −5° and elevate to 30°, which provided a maximum range of . Each mount was elevated and loaded by hand, but the turrets were rotated electrically. The 21 cm gun fired a shell at a muzzle velocity of . At a range of , the armor-piercing shell could penetrate of nickel steel armor; when range fell to , its penetration capabilities increased to . The 21 cm caliber would remain the standard for all subsequent armored cruiser designs.