P-class cruiser

The P class was a German Navy group of twelve heavy cruisers; they were the successor to the s. Design work began in 1937 and continued until 1939; at least nine designs were considered. The final design was armed with six 28 cm quick-firing guns in two triple turrets, as in the preceding Deutschland class. The ships were designated as Panzerschiff (armored ship), and given the preliminary names P1–P12. They were an improved design over the preceding planned D-class cruisers, which had been canceled in 1934. Although the ships were already assigned to shipyards, construction never began on the P-class ships after the design superseded them.

Design
In the early 1930s, Adolf Hitler began a rearmament program in Germany. He signed the Anglo-German Naval Agreement, which allowed Germany to build up its navy to 35 percent of the strength of the British Royal Navy and effectively repudiated the restrictions of the Treaty of Versailles on the German fleet. This led to a decision in 1937 to build ships to an improved design. Design work on the new class of armored ships began that year. After more than twenty designs were considered to meet the navy's specifications, one was chosen; it was designated as cruiser "P". It called for a 20000 t with a maximum speed of 34 to 35 kn, armed with six 28 cm guns in two triple turrets.

By 1938, it became clear to Admiral Erich Raeder that Hitler's aggressive foreign policy would bring conflict with Britain. He therefore decided that a significantly larger force of armored ships would be necessary to execute an effective commerce raiding campaign against the British. Raeder's intention to fight a commerce war against Britain was the basis for Plan Z, which included twelve ships of the P-class design. The design work on the new ships proceeded in parallel with work on the design. Experiments were conducted on at least nine different design proposals between March 1938 and December 1939. The designs varied somewhat in terms of dimensions as well as armament; some of the designs featured three 28 cm triple turrets.

Many problems were encountered with designing the ships, the most prevalent being armor. The required maximum speed of 34 kn meant that the minimum length had to grow from the original 217 m to 229.5 m. It also meant that the beam could be a minimum of 25 m—unless diesel engines, like those used in the Deutschland's, were desired; they would increase the beam by 2 m. Unfortunately for the designers, the widened beam meant that an even longer hull was needed to maintain hydrodynamic efficiency. All of this complicated the armor arrangements, as more armor was needed to cover the longer length and widened beam. Eventually it was deemed that it was impossible to include diesel power on a 20000 t displacement.

Initially, twelve ships were ordered based on the P-class design. The ships were ordered under the provisional names P1 through P12; the contracts were awarded to a number of German shipyards, including Deutsche Werke in Kiel, Blohm & Voss in Hamburg, and the KM Dockyard in Wilhelmshaven. However, Plan Z was reduced in size, and the number of armored ships was pared down to only eight vessels. This caused several of the contracts to be shifted around amongst the various shipbuilding companies. The first keel was set to be laid on 1 Feb 1940. The revised version of Plan Z, approved on 27 July 1939, removed the P-class ships from the construction queue. Instead, the decision was made to build the O-class battlecruisers only.

Characteristics
The P-class ships were 223 m long at the waterline, and 230 m overall. The ships had a beam of 26 m and a designed draft of 7.2 m; the maximum draft was 8 m. They were to have incorporated longitudinal frame stringer steel construction, and would have been primarily welded. The ships would have had thirteen watertight compartments and a transom stern. The ships were equipped with two catapults and two Arado 196 seaplanes. The armor layout was to have used Krupp cemented steel, but the design was not complete; only broad requirements are known. The main armored deck was 70 mm thick, with 100 mm–thick sloping deck armor. The upper deck was 20 mm thick. The two main-battery barbettes had armor protection that ranged between 80 mm and 100 mm thick, and had a depth of 14.2 m. The armored belt was 120 mm thick over the vital areas of the ship, and tapered down to 40 mm in less critical areas.

The ships were designed to be equipped with twelve MAN 9-cylinder V-configuration double acting two-stroke diesel engines that were designed to provide a total of 165,000 shaft horsepower at 250 rpm. The engines were arranged in four sets of three, each of which drove one of four shafts. The shafts each turned a screw that was 4.3 m in diameter. The ships were designed to carry 3600 t of fuel oil, but were capable of storing up to 5000 t. At a cruising speed of 13 knots, this enabled a maximum range of 25,000 nautical miles; at 19 knots, the range was reduced to 15,000 nmi.

The ships were armed with six 28 cm quick-firing guns mounted in two triple turrets, one fore and one aft. It is not known if these were to have been the same 28 cm SK C/28 guns as the preceding Deutschland-class cruisers, or a different design. The ships were also armed with four 15 cm/L55 guns in two twin turrets, also mounted on the centerline, fore and aft. The fore 28 cm turret would have been superfiring over the fore 15 cm turret; the layout was reversed for the aft pair of turrets. The 15 cm twin turrets were Drh L. C/34 mounts—the same type as those fitted to the - and s, as well as a number of other designs. The turrets allowed depression to −10 degrees and elevation to 40 degrees, which enabled a maximum range of 22000 m. The 15 cm guns had a rate of fire of between 6 to 8 45.3 kg rounds per minute, at a muzzle velocity of 875 meters per second (2,871 ft/s). The guns used two propellant charges: a 14.15 kg RPC/38 fore charge and a 23.5 kg main charge in a brass cartridge.

The P-class ships were to have mounted a fairly small anti-aircraft battery: four 10.5 cm/L65 high-angle guns and four 3.7 cm Flak guns. The 10.5 cm guns fired two types of projectiles: a 58.4 kg high explosive shell and a 51.8 kg incendiary round. Both types of ammunition used a single propellant charge: the 11.46 kg RPC/32 charge. The guns could elevate to 80 degrees, and could hit targets 12500 m away. The ships were also armed with six 53.3 cm submerged torpedo tubes.