In the spring of 1934 the Germans began to consider their requirements for further capital ship construction following the building of Gneisenau and her sister. The Treaty of Versailles remained in force, but was being secretly disregarded by the High Command. So when preliminary sketch designs were being discussed, the displacement was already put at 35,000 tons. Early requirements called for a ship of this displacement armed with eight 13in (33.02cm) and twelve 6in (15.24cm) guns, having an armour belt of 350mm and a maximum deck armour of 120mm. There was to be 50mm on the upper deck, 350mm for the barbettes and 400mm for the conning tower, but this scale of protection was impossible to achieve on 35,000 tons and as usual, compromise had to be made. But displacement continued to rise because of a demand that speed be superior to that of the French Dunkerque. After displacement had grown to as much as 37,500 tons, Admiral Raeder specified that 35,000 tons was not in fact to be exceeded, not least because of the problems of the shallow estuaries in the approaches to the main German bases and the need to dock the ships somewhere. By the end of the year the problem was still unresolved in that the demands on the design still required a displacement of 37,200 tons. Despite consideration of turbo-electric and steam options, with either eight 13in (33.02) or 13.7in (35cm) guns, the dimensions of the ship could not be reduced, which was a purely academic state of affairs, because there were no slips large enough for ships of this size. Even so, it was decreed that slip availability was not to be allowed to dictate design parameters, and that water depth and lock gate dimensions (i.e., in the Kiel Canal) would influence the design. In practice this meant a length of no more than 799ft, beam of 119ft and a draught of 33ft. By the beginning of 1935 a published displacement of 35,000 tons had been decided upon, armed with 35cm guns and capable of 28 knots. Germany's position became a little more clear in March that year when Hitler abrogated the Treaty of Versailles, although the fact that other existing treaties limited the displacement of capital ships to 35,000 tons was also tacitly ignored. Displacement was now some 39,000 tons, and in the aftermath of the abrogation of the treaty the main calibre was again increased to 15in (38cm) guns, leading to yet another jump in displacement, this time to 42,500 tons. At this size the ship would be unable to use the largest lock at Wilhelmshaven. This in turn led to various compromises being examined, with comparisons made against the Dunkerque. Inevitably it was found that 15in guns were impossible. In April 1935 the displacement was set at 41,000 tons and the main armament at eight 13.7in (35cm) guns in twin turrets and it was hoped to place an order for the lead ship in one year's time. Then, barely a month later, 15in (38cm) was selected for the main armament, following which there was considerable discussion about the main propulsion plant, both turbo-electric and steam designs being still in the frame. In June 1936 high-pressure steam turbines finally won the day. In the meantime there had been an interminable round of increases and decreases of armour thickness made in compromises to other demands, particularly that of the armament, and it is interesting to note that even casemates were considered for the secondary guns at one stage. The side armour was now reduced to 320mm in thickness. The order for the first ship had in fact already been placed, before the design was finalised, on 16 November 1935, and the modifications made between that date and the summer of the following year when the ship was laid down, caused considerable extra drawing office work.
The final design displaced 41,700 tons standard and 50,900 tons full load, the longitudinally-framed hull, 797ft long, being divided into twenty-two water-tight compartments. Beam to length ratio was 6.71. The protective scheme included a 320mm side belt, which was full thickness for 70 per cent of its depth, tapering at its lower edge to 170mm and backed by 60mm of wood. The depth of this belt was 15ft 10in and it extended between frames 32 and 202, being closed off forward and aft by transverse armoured bulkheads having a maximum thickness (below the main armoured deck) of 220mm. Above this 320mm belt was a 145mm strake which extended for the same length. Aft of the main belt was a shallow 80mm belt which reached as far as the after 150mm armoured bulkhead at frame 105. Forward, the armour belt was 60mm in thickness and reached the stem. These forward and aft belts formed the ship's side plating in these areas. Inboard of the main belt was a longitudinal splinter bulkhead, inclined inwards from top to bottom, the spaces between this and the side belt being normally void. The main torpedo protection was a vertical bulkhead, 45mm thick, which extended from the bottom plating up to the armoured deck. At its maximum the depth of the anti-torpedo protection was just over 20 feet. There were two armoured decks, the upper of which was 50mm, extending from frames 10 to 224. The main deck was 80mm inboard of the torpedo bulkhead and sloped outboard of it at 22° in 110mm thickness (120mm in way of the 15in magazine spaces) to join the side belt towards its lower edge. Aft of the aftermost transverse armoured bulkhead was a lower armoured deck of 110mm which protected the steering gear, while forward the lower deck was only 20mm. Barbette armour was 220mm thick below the upper deck and 340mm above, the 38cm turrets had 360mm fronts, 220mm sides and 130-180mm roofs. Secondary turrets were not as heavily armoured as those in Gneisenau.
The main machinery comprised a triple-shaft geared steam turbine arrangement, with twelve oil-fired Wagner boilers operating at 450°C, 825psi. The boilers were in six separate spaces, each housing two boilers, and occupied two main compartments of the ship, i.e., three units abreast in each. Those for Bismarck were built by Blohm & Voss and for Tirpitz by Deschimag. The main turbines, of Wagner pattern, were built by Blohm & Voss for Bismarck, and by Brown-Boverie for Tirpitz. The wing shafts were powered by the forward turbine rooms, immediately aft of the boiler rooms, and the centre shaft by the aftermost turbine room. Designed power was 163,000shp for a maximum speed of 30 knots.
This class was the first to mount the 15in gun since the First World War Baden, but it was a new design, designated 15in SK C/34, built by Krupp, which fired a l,7641b projectile to a range of 38,880 yards at 30° maximum. The twin turrets were disposed on the centre-line with 'B' and 'C superfiring. Training was electric, elevation hydraulic, with loading at 2.5°. Each turret weighed about 1,047 tons. The secondary armament was designed for LA use and had limited value for barrage HA fire. The 15cm (5.9in) SK C/28 were the same as those carried by Gneisenau but their gunhouses were less heavily armoured. The six twin turrets were shipped three on each beam amidships on the upper deck. Main and secondary batteries could be controlled by any of three directors, which were located in a similar pattern to Gneisenau. The unit on the conning tower had a 7m range-finder, those on the tower and after control, 10m base sets. Each 15in turret had a 10m base RE Heavy AA defence was provided by sixteen 10.5cm (4.1in) in fully stabilised twin 8.8cm LC mountings in four groups of two at shelter deck level. This mounting was the same as that shipped by Gneisenau, i.e., originally designed for the 3.9in gun, but in fact only Bismarck received these, and then only in the four forward (port and starboard) positions because the improved 4.1in mounting (10.5cm LC/37) had become available. Tirpitz received a complete outfit of this mounting which had faster elevation and was of slightly different appearance from the earlier model, though its capabilities were similar. HA fire control was provided by four fully stabilised director range-finders in their distinctive cupolas, one each to port and starboard abreast the tower structure and two on the centre-line aft, one forward and one aft of the after main battery control. There were eight twin 3.7cm disposed as follows: two on 'B' gun deck, two above the navigating bridge, two abreast the after control and two on 'C' gun deck. Finally there were twelve single 2cm. No torpedo tubes were included in the original design. The aircraft installation was originally to have comprised two rotatable catapults on towers abaft the funnel, with no hangar facilities. This was altered so that the ships completed with a double athwartships fixed catapult at upper deck level amidships, with two single hangars abreast the funnel forward of the catapult and a double hangar under the mainmast aft of it. Maximum aircraft stowage was six (which would have included two on the catapults) and the type issued was the Arl96, but in practice no more than four were ever carried because aircraft maintenance on the exposed catapult deck was difficult.
While under construction Bismarck was given an 'Atlantic' bow, and she completed without the foretop and conning tower range-finder positions, the after group of 4.1in guns and the splinter protection domes to the two after HA director-range-finders. The latter were never in fact fitted, but the missing 4.1in guns (in modified LC/37 mountings) were fitted at Gotenhafen together with the foretop and conning tower range-finder positions in October or November 1940. Radar was fitted to the foretop and after range-finders after completion, probably while the ship was at Gotenhafen. The range-finder in 'A' turret was removed after trials, being needed to make up delivery commitments of fire control equipment to the USSR under the German-Soviet Trade Agreement. (Originally it was thought that both 'A' and 'D' turret equipments might have to be sacrificed in both Bismarck and Tirpitz, but Zeiss must have improved deliveries in the end.) As completed, the ship carried twelve single 2cm guns, but in March 1941 one more single in an army-pattern mounting was fitted to the roof of 'A' turret. Two more were fitted around the after command position in April-May 1941 while the ship was in the Baltic. Finally, early in May, two quadruple 2cm were fitted to the searchlight platform on the conning tower and the three single army-pattern mountings were landed. Her relatively early loss precluded further modifications.
Tirpitz received the Atlantic bow prior to launching and completed with all splinter domes to the HA range-finders but without the range-finder in 'A' turret. Early in 1942 she was given two banks of quadruple torpedo tubes, in all probability salvaged from a destroyer sunk at Narvik, and these were fitted on the upper deck just forward of the aftermost 5.9in (15cm) twin mounting. At the same time she received four quadruple 2cm and the singles were increased to fourteen for a total of thirty. After her arrival in Norway, two further quadruple 2cm were added, one on 'B' turret and one on the navigating bridge, the former replacing two singles. Later the singles on the funnel platform were replaced by two more quads and two more fitted abaft 'D' turret. By 1944 her outfit was sixteen quadruple and sixteen singles, but some of the latter may have been converted to twin before her loss. In 1943-4 a Wurzburg height-finding radar set was fitted at the base of the mainmast but removed some time before her sinking.
Bismarck left Hamburg for the first time on 14 September 1940, still lacking many items of equipment, for example range-finders and directors. She went to Kiel where she stayed until 28 September before sailing to the eastern Baltic to work-up. She remained here at Gotenhafen on trials and work-up until 5 December when she went back to Kiel and on to Hamburg for some yard attention. Severe winter weather delayed matters so that it was not until 6 April 1941 that she left Blohm & Voss, never in fact to return. After some further yard work at Kiel, Bismarck returned to Gotenhafen to finish her training. On 1 May, she was inspected by Hitler and on 19 May sailed for Operation 'Rheinubung', a sortie into the Atlantic, in company with the heavy cruiser Prinz Eugen. The German squadron was reported by a Swedish cruiser in the Kattegat, but by 21 May they had reached Korsfiord near Bergen. The two ships left the same day and sailed north, passing down the Denmark Strait between Iceland and Greenland to reach the Atlantic. Shadowed by British cruisers, on leaving the strait they were intercepted by the British battle-cruiser Hood and battleship Prince of Wales on the morning of 24 May 1941. In the brief action that followed, Hood, hit by several 15in shells, blew up and sank with only three survivors, and the new Prince of Wales broke off the action with damage. Bismarck was hit three times by 14in shells from Prince of Wales, one of which caused extensive flooding forward and, more importantly, rendered inaccessible or unusable some 1,000 tons of oil fuel. A second hit damaged a generator room and boiler room. The third was unimportant. A huge hunt was now launched against the German ships but Prinz Eugen was successfully detached unobserved that evening, while the flagship continued alone towards Brest. An air strike sent against them from Victorious towards midnight on 24 May resulted in one hit on Bismarck's armour belt which caused no damage, except that her manoeuvring increased the flooding caused by the action in the Denmark Strait and one boiler room had to be closed down. Early on the morning of 25 May the shadowing cruisers lost contact, but she was spotted by a Catalina in mid-morning on 26 May. Another air strike was launched against her, this time from Ark Royal, whose force of fifteen Swordfish found their target later that night. Two or possibly three torpedoes hit, one of which, striking aft, proved decisive, having jammed the steering. Bismarck was now only able to steam in circles - despite mammoth efforts to free the rudders, all attempts failed. By midnight the British 4th Destroyer Flotilla (which included one Polish ship) had made contact and for the next six hours or so made torpedo attacks until all were expended but achieved no hits, while the battleship was equally unsuccessful in hitting her opponents. During the morning of 27 May the British battleships King George V and Rodney gained contact and in an action lasting a couple of hours Bismarck was reduced to a wreck. She finally sank, either as a result of torpedoes from the cruiser Dorsetshire or from her own scuttling charges.
Tirpitz, having escaped the concerted efforts of the RAF to destroy her while under construction, commissioned at Wilhelmshaven on 25 February 1941 and ran preliminary trials in the Scheerhafen until sailing for Kiel on 9 March, reaching Gotenhafen in the eastern Baltic on 14 March to begin work-up. This continued until January 1942, interrupted only by a brief deployment (23-25 September) to the Aaland Islands as part of the Baltenflotte, formed in September, against the possibility of a break-out by the Soviet fleet in Leningrad after the German invasion of Russia a couple of months earlier. When it became obvious that the Soviet Fleet was not going to come out, Tirpitz sailed west on 12 January 1942 and, escorted by destroyers, made passage for Norway, arriving in Assenfiord near Trondheim by the 17th. Apart from a brief trip to the entrance to the fiord on 21 February for the purpose of supporting the arrival of Prinz Eugen and Admiral Scheer, her activities were limited to training until she sortied to attack convoy PQ12 on 6 March. Failing to find it and having evaded British air attacks, she put into Narvik on the 9th and had returned to Trondheim by the 13th. On 2 July she sailed again, this time to attack PQ13, accompanied by Admiral Scheer and Admiral Hipper as well as destroyers (Lutzow had run aground). Vacillation in high places delayed the ships' departure until 5 July, and then, because of the U-boat successes already achieved, it was decided that surface attack would not be required and they returned to harbour at Kaafiord. Tirpitz remained in Arctic waters as the core of the 1st Battle Group, acting mostly as a 'fleet in being', tying down the British Home Fleet and wasting the RAF's time, without putting to sea. On 11 March 1943 she moved to Bogen Bay, arriving on the 13th, but by the 24th she was back in Altenfiord. Not until 6-9 September did she mount another offensive operation, this time in company with Scharnhorst, for an attack on the Island of Spitzbergen. On 22 September she was very badly damaged in an attack by British X-craft midget submarines. Repairs under the difficult and limited conditions in Altenfiord took until mid March 1944 after which she began trials. While still so engaged she was again badly damaged on 3 April by a force of naval aircraft from the British carriers Victorious and Furious. Hit by fourteen bombs, the ship's superstructure was decimated but the armoured deck was not penetrated. Another attack by RAF Lancasters from a base in Russia on 15 September using Tallboy 6-ton bombs achieved one hit in the bows which caused severe shock damage, buckled the hull and lifted machinery off its foundations. The resultant damage was so bad that the ship was finished as a fighting unit and, after temporary repairs, she steamed slowly to a berth inshore near Tromso, where she arrived on 16 October. Her role was reduced to that of a floating battery, but now in range of home-based RAF bombers, she was attacked on 29 October but sustained no major damage, and again on 12 November when, hit and near-missed by several Tallboys, she blew up and capsized. The wreck was broken up in situ post-war.