Seydlitz was a heavy cruiser of the German Kriegsmarine, fourth in the Admiral Hipper class, 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 completion and work was finally stopped in the summer of 1940 when she was approximately 95 percent. The unfinished ship remained inactive 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.