The class was a series of three (armored ships), a form of heavily armed cruiser, built by the (Germany navy) officially in accordance with restrictions imposed by the Treaty of Versailles. The ships of the class, , , and , were all stated to displace in accordance with the Treaty, though they actually displaced at standard displacement. The design for the ships incorporated several radical innovations, including the first major use of welding in a warship and all-diesel propulsion. Due to their heavy armament of six guns and lighter weight, the British referred to the vessels as "pocket battleships". The -class ships were initially classified as , but the (the renamed German navy) reclassified them as heavy cruisers in February 1940.
The three ships were built between 1929 and 1936 by the Deutsche Werke in Kiel and the in Wilhelmshaven, seeing much service with the German Navy. All three vessels served on non-intervention patrols during the Spanish Civil War. While on patrol, was attacked by Republican bombers, and in response, bombarded the port of Almería. In 1937, represented Germany at the Coronation Review for Britain's King George VI. For the rest of their peacetime careers, the ships conducted a series of fleet maneuvers in the Atlantic and visited numerous foreign ports in goodwill tours.
Before the outbreak of World War II, and were deployed to the Atlantic to put them in position to attack Allied merchant traffic once war was declared. remained in port for periodic maintenance. was not particularly successful on her raiding sortie, during which she sank or captured three ships. She then returned to Germany, where she was renamed . sank nine vessels in the South Atlantic before she was confronted by three British cruisers at the Battle of the River Plate. Although she damaged the British ships, she was herself damaged and her engines were in poor condition. Coupled with deceptive false British reports of reinforcements, the state of the ship convinced Hans Langsdorff, her commander, to scuttle the ship outside Montevideo, Uruguay.
and were deployed to Norway in 1942 to join the attacks on Allied convoys to the Soviet Union. conducted Operation Wunderland in August 1942, a sortie into the Kara Sea to attack Soviet merchant shipping, though it ended without significant success. took part in the Battle of the Barents Sea in December 1942, a failed attempt to destroy a convoy. Both ships were damaged in the course of their deployment to Norway and eventually returned to Germany for repairs. They ended their careers bombarding advancing Soviet forces on the Eastern Front; both ships were destroyed by British bombers in the final weeks of the war. was raised and sunk as a target by the Soviet Navy, and was partially broken up in situ, with the remainder of the hulk buried beneath rubble.
Development
Following Germany's defeat in World War I, the size of the German Navy, renamed the , was limited by the Treaty of Versailles. The Navy was permitted a force of six pre-dreadnought battleships and six light cruisers; the ships could not be replaced until they were twenty years old. To replace the battleships, new vessels were to displace at most ; Germany's potential rivals were at this time limited to building vessels of by the Washington Naval Treaty and subsequent agreements. The gun caliber of any new ship was not regulated by the Treaty itself, though the Naval Inter-Allied Commission of Control (NIACC) created by the Treaty did have authority to regulate the armament of all new warships. The Allies assumed that with these limitations, only coastal defense ships similar to those operated by the Scandinavian navies could be built.
The s oldest battleship, , was laid down in 1902 and could therefore be replaced legally in 1922. Design studies were considered starting in 1920, with two basic options: the Navy could build a heavily armored, slow, and small warship similar to a monitor, or a large, fast, and lightly armored vessel similar to a cruiser. Actual design work on the new type of armored ship began in 1923, but the economic collapse forced a temporary halt to the work. Admiral Hans Zenker, the commander in chief of the , pushed hard for the navy to resume design work, and in 1925 three new proposals were drafted. In addition to two sketches prepared in 1923, this totaled five different designs. Of the first two designs, "I/10" was a cruiser armed with eight guns while "II/10" was a , heavily armored ship armed with four guns. The three designs prepared in 1925—"II/30", "IV/30", and "V/30"—were armed with six guns with varying levels of armor protection. The eventually opted for guns to avoid provoking the Allies and to ease pressures on the design staff.
The held a conference to evaluate the designs in May 1925, though the results were inconclusive. Of particular importance was the continued French occupation of the Ruhr industrial area, which prevented Germany from quickly building large-caliber artillery. Nevertheless, the design staff prepared another set of designs, "I/35", a heavily armored ship with a single triple turret forward, and "VIII/30", a more lightly-armored ship with a pair of twin turrets. The initially intended to lay down the first armored ship in 1926, but the design had not yet been finalized. The 1926 maneuvers informed the design staff that greater speed was desirable, and that year, a further two designs were submitted to Zenker. The initial design for , ordered as " A", was prepared in 1926 and finalized by 1928. Zenker announced on 11 June 1927 that the Navy had settled on one of several proposals for the new warships. The had decided that the new ships would be armed with two triple turrets mounting 28 cm guns.
Political opposition to the new ships was significant. The therefore decided to delay ordering the ship until after the elections in 1928. The question over whether to build the new ships was a major issue in elections, particularly with the Social Democrats, who strongly opposed the new ships and campaigned with the slogan "Food not ." In May 1928, the elections were concluded and enough of a majority in favor of the new ships was elected; this included twelve seats won by Adolf Hitler's Nazi Party. An October 1928 attempt by the Communist Party of Germany to initiate a referendum against the construction failed. The first of the new ships was authorized in November 1928.
When the particulars of the design became known by the Allies, they attempted to prevent Germany from building them. The offered to halt construction on the first ship in exchange for admittance to the Washington Treaty with a ratio of to Britain's allotment of of capital ship tonnage. In doing so, this would effectively abrogate the clauses in the Treaty of Versailles that limited Germany's naval power. Britain and the United States favored making concessions to Germany, but France refused to allow any revisions to the Treaty of Versailles. Since the ships did not violate the terms of the Treaty, the Allies could not prevent Germany from building them after a negotiated settlement proved unattainable.
Design
General characteristics
The three -class ships varied slightly in dimensions. All three ships were long at the waterline, and as built, long overall. and had clipper bows installed in 1940–1941; their overall length was increased to . had a beam of , s beam was , while s was . and had a standard draft of and a full-load draft of . s draft was and , respectively. The displacement of the three ships increased over the class. Standard displacement grew from for to for and for . The ships' full load displacements were significantly higher, at for , for , and for . The ships were officially stated to be within the limit of the Treaty of Versailles, however.
The ships' hulls were constructed with transverse steel frames; over 90 percent of the hulls used welding instead of the then standard riveting, which saved 15 percent of their total hull weight. These savings allowed the armament and armor to be increased. The hulls contained twelve watertight compartments and were fitted with a double bottom that extended for 92 percent of the length of the keel. As designed, the ship's complement comprised 33 officers and 586 enlisted men. After 1935, the crew was dramatically increased, to 30 officers and 921–1,040 sailors. While serving as a squadron flagship, an additional 17 officers and 85 enlisted men augmented the crew. The second flagship had an additional 13 officers and 59 sailors. The ships carried a number of smaller boats, including two picket boats, two barges, one launch, one pinnace, and two dinghies.
The considered the ships to be good sea boats, with a slight roll. As built, they were wet in a head sea, though this was significantly improved by the installation of a clipper bow in 1940–1941. The ships were highly maneuverable, particularly when the maneuvering setting for the diesel engines was used, in which half of the engines for each shaft were run in reverse. The ships heeled over up to 13 degrees with the rudder hard over. The low stern was wet in a stern sea, and equipment stored there was frequently lost overboard.
Machinery
The -class ships were equipped with two sets of four 9-cylinder, double-acting, two-stroke diesel engines built by MAN. The adoption of an all-diesel propulsion system was a radical innovation at the time and contributed to significant savings in weight. Each set was controlled by transmissions built by AG Vulcan. The engines were paired on two propeller shafts, which were attached to three-bladed screws that were in diameter. was initially fitted with diameter screws, before they were replaced with the larger screws. The engines were rated at and a top speed of . They did not meet the expected shaft-horsepower on trials, though they did exceed their design speeds. s engines reached and , and s engines reached and . Horsepower figures for are not recorded, though her top speed on trials was .
could carry up to of fuel oil, which provided a maximum range of at a speed of . An increase in speed by one knot reduced the range slightly to . At a higher speed of , the range fell to . carried and had a correspondingly shorter range of at 20 kn. stored of fuel, which enabled a range of . Electricity was supplied by four electric generators powered by two diesel engines. Their total output was 2,160 kW for , 2,800 kW for , and 3,360 kW for , all at 220 volts. Steering was controlled by a single rudder.
Armament
The three -class ships were armed with a main battery of six 28 cm SK C/28 guns mounted in two triple turrets, one on either end of the superstructure. The turrets were the Drh LC/28 type and allowed elevation to 40 degrees, and depression to −8 degrees. This provided the guns with a maximum range of . They fired a projectile at a muzzle velocity of . The guns were initially supplied with a total 630 rounds of ammunition, and this was later increased to 720 shells.
The secondary battery comprised eight 15 cm SK C/28 guns, each in single MPLC/28 mountings arranged amidships. These mountings allowed elevation to 35 degrees and depression to −10 degrees, for a range of . They were supplied with a total of 800 rounds of ammunition, though later in their careers this was increased to 1,200 rounds. These shells weighed and had a muzzle velocity of .