The H class was a series of battleship designs for Nazi Germany's , 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 s with guns and diesel propulsion. The "H-41" design improved the "H-39" ship with still larger main guns, eight weapons, and reinforced deck armor. The Construction Office of the (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 pieces, and the enormous "H-44" design ultimately resulted with guns. The ships ranged in size from the "H-39", which was long on a displacement of , to the "H-44", at on a displacement of . Most of the designs had a proposed top speed in excess of .
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.
Initial design
The earliest design studies for " H" ("Battleship H") date to 1935, and were near repeats of the early designs for the ships, armed with guns. Intelligence indicating that the Soviet Navy was planning the with guns prompted the Germans to increase the caliber of the ship's armament to 38 cm as well on 5 October 1936. The (OKM) issued staff requirements at the end of October for a ship of armed with eight 38 cm guns with a speed of . The ship's radius of action was to be at least equal that of the s.
Design work on the ship that came to be designated H-39 began in 1937. The design staff was instructed to improve upon the design for the preceding class; one of the requirements was a larger-caliber main battery to match any battleship built by a potential adversary. After Japan refused to ratify the Second London Naval Treaty in April 1936, an escalator clause went into effect that permitted signatories to arm battleships with guns of up to caliber, something the United States Navy announced it would do with its planned s. By virtue of the Anglo-German Naval Agreement, signed in 1935, Germany was considered to be a party to the other international naval arms limitation treaties.
Admiral Werner Fuchs, responsible for the staff section in the OKM that determined the operating requirements for the ship, discussed the vessel's design with Adolf Hitler, the leader of Germany. Hitler demanded guns larger than any possible adversary, but guns of the caliber demanded by Hitler would have required displacements of over and drafts so deep as to prevent the use of Germany's ports without significant dredging. Fuchs eventually convinced Hitler that the 40.6 cm gun was the optimal choice for the H-39 design. In 1938, the OKM developed Plan Z, the projected construction program for the German navy. A force of six H-39 class battleships was the centerpiece of the fleet. Plan Z was finalized by January 1939, when Admiral Erich Raeder, the commander of the , presented it to Hitler. He approved the plan on 18 January and granted the unlimited power to bring the construction program to fruition.
Only four shipyards in Germany had slipways large enough to build the six new battleships. The OKM issued orders for construction of the first two ships, "H" and "J", on 14 April 1939. The contracts for the other four ships, "K", "L", "M", and "N", followed on 25 May. The keels for the first two ships were laid at the Blohm & Voss dockyard in Hamburg and the shipyard in Bremen on 15 July and 1 September 1939, respectively. The outbreak of war in September 1939 interrupted the construction of the ships. Work on the first two was suspended and the other four were not laid down, as it was believed they would not be finished before the war was over. The keel for "H" had of steel installed, of steel had been machined, out of of steel supplied to Blohm & Voss by that point. Only of steel had been worked into the keel for "J", out of of steel delivered. Steel for the other four ships had been ordered and partially machined for installation, though no assembly work had begun. It was expected to resume work on the ships after a German victory in the war.