Prinz Adalbert - class cruiser The " Prinz Adalbert " class was a type of armored cruiser built for the Imperial German Navy in the early 1900s . Two ships of the class were built , , and . " Friedrich Carl " was commissioned first , on 12 December 1903 and " Prinz Adalbert " followed on 12 January 1904 . They were an improvement upon the design of the previous unique armored cruiser , . Their armor belt s were the same thickness but were more extensive than that of their predecessor . The two ships were also armed with four main guns in twin gun turrets , as opposed to the two single gun turrets of " Prinz Heinrich " . Both ships saw extensive service with the German Navy ; " Prinz Adalbert " was used as a gunnery training ship for the entirety of her peacetime career , while " Friedrich Carl " served with the fleet until 1909 , when she was withdrawn to act as a torpedo training vessel . At the outbreak of World War I in August 1914 , both vessels were mobilized and assigned to the cruiser squadron in the Baltic . " Friedrich Carl " was sunk by Russian naval mines off Memel in November 1914 , though most of her crew was safely evacuated . " Prinz Adalbert " was torpedoed twice by British submarines operating in the Baltic ; the first , on 1 July 1915 , caused serious damage that was ultimately repaired . The second , on 23 October 1915 , caused a catastrophic explosion in the ship ' s ammunition magazines that destroyed the ship . Six - hundred and seventy - two men were killed , the greatest single loss of life for the German Navy in the Baltic during the war . Design . The Second Naval Law in Germany , passed in 1900 , envisioned a force of fourteen armored cruiser s intended for overseas service in the German colonies . However , the German Navy required cruisers for operations with the fleet as well , and attempted to design ships that could fulfill both roles , primarily due to budget constraints . The first product of the 1900 Naval Law , , was an alteration of an earlier vessel , , equipped with fewer guns and thinner armor in a trade - off for higher speed and lower cost . The subsequent design — that of the " Prinz Adalbert " class — prepared in 1899 – 1900 , was an improvement on " Prinz Heinrich " . Four quick - firing guns were substituted for the pair of slower guns mounted on the older vessel . Armor thickness remained similar in strength to that of " Prinz Heinrich " , though it was made more comprehensive . General characteristics . The ships of the " Prinz Adalbert " class were long at the waterline and overall , and had a beam of . The ships were designed to displace , but at full combat 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 . The German navy 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 . They lost up to 60 percent speed with the rudder hard over , but suffered only minimal speed loss in heavy seas . The ships ' casemate guns were placed too low , which rendered them exceedingly wet even in a slight swell . They had a transverse metacentric height of . 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 nine 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 . " Prinz Adalbert " and " Friedrich Carl " 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 Dürr boilers produced by " Düsseldorf - Ratinger Röhrenkesselfabrik " . 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 . " Prinz Adalbert " and " Friedrich Carl " were armed with a main battery of four SK L / 40 guns in two twin turrets , one on either end of the main superstructure . The four guns were supplied with a total of 340 rounds of ammunition , or 85 shells per gun . The turrets could depress to −5° and elevate to 30° , which provided a maximum range of . The 21 cm gun fired a shell at a muzzle velocity of per second . The ships ' secondary armament consisted of ten SK L / 40 guns , all placed in the sides of the hulls . Three guns were mounted in casemates amidships on either side , with a pair of gun turrets above them . These guns were provided with a total of 1 , 400 shells , or 140 per gun . These guns fired an projectile at a muzzle velocity of per second . The guns could elevate to 30° , allowing a maximum range of . The ships also carried twelve 8 . 8 cm SK L / 35 guns for close in defense ; these were arranged in groups of four in shielded pivot mounts . Four guns were mounted around the forward conning tower , four were emplaced around the rear two funnels amidships , with the last four guns placed on top of the rear superstructure . These guns fired a shell at a muzzle velocity of per second . They could elevate to 25° and could engage targets out to . The vessels ' armament system was rounded out by four submerged torpedo tubes . They were mounted in the bow , stern , and on each broadside , and supplied with eleven torpedoes . Armor . The steel armor used on the two ships was produced by the Krupp firm . The main belt armor consisted of a layer of teak that was thick , covered by thick steel plating in the central section , which covered the ships ' machinery spaces and ammunition magazines . The belt was reduced to on either ends of the central portion ; the bow and stern were unprotected . The armored deck ranged in thickness from to 80 mm . Sloped armor , which ranged in thickness from 50 to 80 mm , connected the deck to the armored belt . The ships ' casemate guns , which were placed above the main belt , were protected by 100 mm thick armor plating , as were the 15 cm turret guns . The two 21 cm guns had 150 mm thick sides and 30 mm roofs . The forward conning tower was protected by sides and had a thick roof . The rear conning tower was much less thoroughly protected , with only worth of armor protection . Service history . " Prinz Adalbert " was laid down at the Imperial Dockyard in Kiel in 1900 , under construction number 27 . She was ordered under the contract name " B " . The completed hull was launched on 22 June 1901 , after which fitting - out work was effected . The ship was finally completed by 12 January 1904 , the day she was commissioned into the German Navy . " Friedrich Carl " was ordered as " Ersatz König Wilhelm " and assigned to the Blohm & Voss shipyard ; her keel was laid in 1901 . She was launched on 21 June 1902 , almost exactly a year after her sister ship . After fitting out work was completed , " Friedrich Carl " was commissioned into the Navy on 12 December 1903 , a month before her sister ship . " Prinz Adalbert " went into service as a gunnery training vessel for the fleet after her commissioning , while " Friedrich Carl " served with the cruiser division of the battle fleet . In 1909 , " Friedrich Carl " joined her sister ship as a training vessel , being used as a torpedo training ship . The two ships were re - mobilized after the outbreak of World War I in August 1914 . Both ships were assigned to Admiral Behring ' s cruiser squadron in the Baltic Sea , with " Friedrich Carl " serving as his flagship . The squadron was based in Neufahrwasser in Danzig . Behring was ordered to undertake actions against the Russian port of Libau , which was believed to be acting as a staging area for British submarines . On the first assault on the port , on 17 November 1914 , " Friedrich Carl " struck a pair of Russian naval mine s off Memel . The ship ' s crew managed to keep the cruiser afloat long enough to allow nearby vessels to take off the entire crew ; only seven men were killed in the attack . The operation proceeded as planned , however , and several blockships were sunk in the harbor entrance . After the sinking of " Friedrich Carl " , Behring shifted his flag to " Prinz Adalbert " . The ship conducted several operations against Russian forces , including bombardments of Libau . In May 1915 , she supported the German Army attack that captured the city . On 1 July 1915 , the ship sortied to reinforce a German minelaying operation that had come under attack by a Russian cruiser flotilla . While en route with the armored cruiser , " Prinz Adalbert " was torpedoed by the British submarine . The damage was severe , though the cruiser was able to return to Kiel for repairs . Repairs were finally completed by October 1915 . " Prinz Adalbert " was steaming some 20 miles west of Libau in company with a pair of destroyers on 23 October when she was intercepted by the submarine . " E8 " fired a spread of torpedoes at a range of approximately 1 , 200 m ( 1 , 300 yd ) , which detonated the ship ' s ammunition magazine . The massive explosion destroyed the ship , which sank immediately with the loss of 672 crew . There were only three survivors . The sinking was the greatest single loss of life for the German Baltic forces for the duration of the war .