The H class was a series of battleship designs for Nazi Germany's Kriegsmarine, which were intended to fulfill the requirements of Plan Z in the late 1930s and early 1940s. The first variation, "H-39," called for six ships to be built, essentially as enlarged Bismarck-class battleships with 40.6 cm (16 in) guns and diesel propulsion. The "H-41" design improved the "H-39" ship with still larger main guns, eight 42 cm (16.5 in) weapons, and reinforced deck armor. The Construction Office of the Oberkommando der Marine (OKM) concluded their work with the "H-41" design, and were not involved in subsequent plans. Two of them, "H-42" and "H-43", increased the main battery yet again, with 48 cm (18.9 in) pieces, and the enormous "H-44" design ultimately resulted with 50.8 cm (20 in) guns. The ships ranged in size from the "H-39", which was 277.8 m (911 ft 5 in) long on a displacement of 56,444 t (55,553 long tons), to the "H-44", at 345 m (1,131 ft 11 in) on a displacement of 131,000 t (129,000 long tons). Most of the designs had a proposed top speed in excess of 30 knots (56 km/h).
Due to the outbreak of World War II in September 1939, none of the ships were ever completed; only the first two of the "H-39" ships were laid down. What work that had been accomplished was halted; the assembled steel remained on the slipway until November 1941, when the OKM ordered it be sent for scrap and used for other purposes. Contracts for the other four "H-39" type ships had been awarded, but no work was begun on any of them before they were canceled. None of the subsequent designs progressed further than planning stages.(more on Wiki HERE)