German cruiser Seydlitz
was a heavy cruiser of Nazi Germany's , fourth in the , but was never completed. The ship was laid down in December 1936 and launched in January 1939, but the outbreak of World War II slowed her construction and fitting-out work was finally stopped in the summer of 1940 when she was approximately 95 percent complete. The unfinished ship remained pier-side in the shipyard until March 1942, when the  decided to pursue aircraft carriers over surface combatants. was among the vessels chosen for conversion into auxiliary aircraft carriers. Renamed , the ship was to have had a complement of ten Bf 109 fighters and ten Ju 87 divebombers. Work lasted from 1942 to 1943, but was not completed, and the incomplete vessel was towed to Königsberg in early 1944. She was eventually scuttled there in 1945 as the Soviet Red Army approached the city. The wreck was seized by the Soviets and was briefly considered for cannibalization for spare parts to complete her sistership  for the Soviet Navy. This plan was also abandoned, and the ship was broken up for scrap. Design 

The  of heavy cruisers was ordered in the context of German naval rearmament after the Nazi Party came to power in 1933 and repudiated the disarmament clauses of the Treaty of Versailles. In 1935, Germany signed the Anglo–German Naval Agreement with Great Britain, which provided a legal basis for German naval rearmament; the treaty specified that Germany would be able to build five  "treaty cruisers". The s were nominally within the 10,000-ton limit, though they significantly exceeded the figure. was  long overall and had a beam of  and a maximum draft of . The ship had a design displacement of  and a full load displacement of . was powered by three sets of geared steam turbines, which were supplied with steam by twelve ultra-high pressure oil-fired boilers. The ship's top speed was , at . As designed, her standard complement consisted of 42 officers and 1,340 enlisted men. s primary armament was eight  SK L/60 guns mounted in four twin gun turrets, placed in superfiring pairs forward and aft. Her anti-aircraft battery  consisted of twelve  L/65 guns, twelve  guns, and eight  guns. The ship also carried a pair of triple  torpedo launchers abreast of the rear superstructure. The ship was equipped with three Arado Ar 196 seaplanes and one catapult. s armored belt was  thick; her upper deck was  thick while the main armored deck was  thick. The main battery turrets had  thick faces and 70 mm thick sides. Construction and conversion 

 was ordered by the  from the  shipyard in Bremen. was originally designed as a light cruiser version of the -class heavy cruisers, armed with twelve  guns instead of the s eight 20.3 cm guns. The  decided, however, to complete the ship identically to  on 14 November 1936. Her keel was laid on 29 December 1936, under construction number 940. The ship was launched on 19 January 1939, and at the launching ceremony, Admiral Richard Foerster, who had been the gunnery officer of the namesake ship, gave a speech, and the widow of that ship's commander during World War I christened the vessel. At that time, her hull had been completed with a straight stem. After the outbreak of World War II in September 1939, work slowed considerably as priorities shifted to vessels that could be completed faster, like destroyers, U-boats, and smaller craft. Nevertheless, work on the ship proceeded at a slow pace, and during this period her bow was altered to the standard "Atlantic bow" that had been installed on her sister ships. By the time work stopped completely in June 1942, the ship was approximately 95 percent complete; only her anti-aircraft armament, masts, cranes, and her aircraft catapult remained to be installed. Following the loss of the battleship  in May 1941, during which British aircraft carriers proved instrumental, and the near torpedoing of her sistership  in March 1942, the Kriegsmarine became convinced of the necessity of acquiring aircraft carriers. Work on the purpose-built carrier , which had been halted in April 1940, was resumed in March 1942. The Kriegsmarine also decided to convert a number of vessels into auxiliary aircraft carriers. was among the ships selected for conversion, along with several passenger liners. These included , , and . The unfinished French cruiser  was also to be converted. As the design staff examined the existing ships, they determined that  and  were too slow, and  would only be suitable as a training carrier, so only  and  would be completed as front-line carriers. The navy envisioned operating the carriers from northern Norway to interdict the supply convoys to the Soviet Union. At the same time as construction of  resumed, conversion work began on . The majority of the superstructure was cut away, with the exception of the funnel, to prepare for the installation of a flight deck and an aircraft hangar. In total, approximately  of material from the ship was removed. The ship was renamed , but work was ceased in June 1943, before the conversion was completed. By that time, her superstructure had been entirely razed to the upper deck, apart from her funnel. As British and American air raids increased in intensity through 1943, the Germans decided to move the ship to Königsberg in an attempt to place her out of the reach of Allied bombers. She could not be moved until March 1944, however, when she was towed to Kiel. She was then towed from Kiel to Königsberg between 30 March and 2 April. She remained there for the rest of the war, and likely little work was done; in December, she was classified as a hulk. On 29 January 1945, the ship was scuttled before the advancing Soviet Red Army could seize her. The Soviet Navy nevertheless considered using the wreck for parts to complete the cruiser , a sister-ship of  the Soviets had purchased unfinished before the outbreak of war. This was not carried out, however, and the ship was eventually raised before being broken up beginning in 1958. Specifications

The conversion work would have slightly increased the ship's length to  long overall, but decreased her draft to  at full load. Her propulsion system, which had already been installed, would remain the same, as would her expected performance. A large island was to be installed on the starboard side, with a tall, tubular mast on the forward end of the island. The flight deck was to have been  long and  wide. The hangar was  long and  wide forward and  wide amidships and aft. Two elevators would have been installed to transfer aircraft from the hangar to the flight deck. s air complement was to have consisted of ten Bf 109 fighters and ten Ju 87 Stuka divebombers. The Bf 109 fighters were a navalized version of the "E" model, designated as Bf 109T. Their wings were longer than the land-based model to allow for shorter take-off. The Ju 87 type selected was to have been the "E" variant, which was a navalized version of the Ju 87D, and were modified for catapult launches and were equipped with arresting gear. Armament
Her armament was reduced to a medium-caliber anti-aircraft battery of ten 10.5 cm L/65 guns in twin mounts, two forward of the conning tower and three aft. All of these would have been in line with the island, in a superfiring arrangement. The LC/31 mounting was triaxially stabilized and capable of elevating to 80°. This enabled the guns to engage targets up to a ceiling of . Against surface targets, the guns had a maximum range of . The guns fired fixed ammunition weighing ; the guns could fire HE and HE incendiary rounds, as well as illumination shells. These would have been supported by a battery of light anti-aicraft guns consisting of ten 3.7 cm guns in dual mounts and twenty-four 2 cm guns in quadruple mounts. These were distributed along the sides of the ship, generally on platforms that overhung the sides of the ship. Four of the 3.7 cm mounts were on the sides of the ship and the fifth mount was on the extreme bow. Two of the 2 cm mounts were to be placed on the island, with the remainder in the side platforms. The mounts were the Dopp LC/31 type, originally designed for earlier  SK C/31 guns. The 3.7 cm gun was a single-shot gun, with a rate of fire of around 30 rounds per minute. At its maximum elevation of 85°, the gun had a ceiling of . The 2 cm gun was a magazine-fed automatic weapon, firing at up to 500 rounds per minute. Twenty and forty-round magazines were supplied for the guns;

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References 

 
 
 
 
 
 
 
 
 
 
 

Admiral Hipper-class cruisers
Ships built in Bremen (state)
1939 ships
World War II cruisers of Germany
World War II aircraft carriers of Germany
World War II shipwrecks in the Baltic Sea
Germany–Soviet Union relations
Maritime incidents in April 1945
Proposed ships of Germany