German cruiser Seydlitz Seydlitz was a heavy cruiser of the German Kriegsmarine , 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 Kriegsmarine decided to pursue aircraft carriers over surface combatants . " Seydlitz " was among the vessels chosen for conversion into auxiliary aircraft carriers . Renamed " Weser " , the ship was to have had a complement of ten Bf 109 fighters and ten Ju 87 divebombers . Work was not completed , however , and the incomplete vessel was towed to Königsberg where she was eventually scuttled . The ship was seized by the advancing Soviet Army 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 . Construction . " Seydlitz " was ordered by the Kriegsmarine from the Deschimag shipyard in Bremen . " Seydlitz " was originally designed as a light cruiser version of the heavy cruiser s , armed with twelve guns instead of the " Admiral Hipper " s eight guns . The Kriegsmarine decided , however , to complete the ship identically to " Admiral Hipper " on 14 November 1936 . Her keel was laid on 29 December 1936 , under construction number 940 . The ship was launched on 19 January 1939 , but after the outbreak of World War II in September 1939 , work was halted when the ship was approximately 95 percent complete . " Seydlitz " 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 . " Seydlitz " 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 . " Seydlitz " s primary armament was eight SK L / 60 guns mounted in four twin gun turret s , 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 . " Seydlitz " 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 . Conversion . 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 . " Seydlitz " was among the ships selected for conversion , along with several passenger liners . At the same time as construction of " Graf Zeppelin " resumed , conversion work began on " Seydlitz " . 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 flight deck was to have been long and wide . The hangar was long and wide forward and wide amidships and aft . Her armament was reduced to an anti - aircraft battery of ten 10 . 5 cm L / 65 guns in twin mounts , two forward of the conning tower and three aft , ten 3 . 7 cm guns in dual mounts , and twenty - four 2 cm guns in quadruple mounts . " Seydlitz " 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 87s were 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 . The ship was renamed " Weser " , but work was ceased in June 1943 , before the conversion was completed . The unfinished vessel was then transferred to Königsberg , where she remained for the rest of the war . 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 " Seydlitz " the Soviets had purchased before the outbreak of war . This was not carried out , however , and the ship was broken up for scrap . Footnotes . Notes Citations