The Bismarck class battleships were a class of battleships built by Germany around the onset of World War II. In terms of full-load displacement, the Bismarck-class ships were the third-largest battleships ever completed, behind the Japanese Yamato class and the American Iowa class.
According to the prewar German naval program, Plan Z, the Bismarcks were to operate in conjunction with Scharnhorst battleships (considered battlecruisers by the British) as a homefleet set against the Royal Navy. Operationally, they had to be used in attacking merchant shipping, because the planned H-class battleships were still nowhere near completion when hostilities commenced. Both Bismarck-class ships were sunk during the Second World War. Bismarck was sunk in combat with the Royal Navy in the North Atlantic. The Tirpitz capsized at its anchorage in Norway after an aerial attack from Royal Air Force bombers.
In reality, both were considerably heavier, weighing in at 42,000 tons. Although Bismarck and Tirpitz were nearly identical insofar as basic configuration and dimensions, Bismarck has become something of a naval legend while Tirpitz led a comparatively unglamorous life.
The Bismarck class embodied much of what made Germany's World War I battleships outstanding combat vessels, and their design was broadly influenced by the last German battleship classes of World War I. The general disposition of the main battery, armour, and machinery was similar to the Bayern class.
However, the Bismarck also represented the limitations of practical design experience, as well as the compromises forced by designing individual large warships that were arrayed against a numerically superior adversary. The most serious problems were the location of fire-control systems, particularly for the anti-aircraft battery; the inability of the Germans to develop a suitable diesel propulsion system (a problem not limited to the German Navy); and the general weakness of the mixed-calibre secondary battery against aerial attack (which was mirrored in contemporary Italian, Japanese, and Soviet capital ship designs). While the preceding Kaiserliche Marine of World War I had an established institution of expert designers, it was effectively disbanded following Germany's surrender. The reformed Kriegsmarine was thus disadvantaged, but the Bismarck and Tirpitz were generally well-regarded ships, being a reasonable example of design compromise, and suited to the European theatre of operations.
The original design for the warships provisionally dubbed F and G (the Bismarck and Tirpitz, respectively) was as a fast commerce raider with 33cm guns, and slightly thicker armour than was eventually used on Bismarck. Crucially the machinery was intended to be diesels, giving a range of 16000 nmi at 21 knots, which would have permitted 5 week cruises. This would have allowed the ships to criss-cross the North Atlantic in search of targets, even allowing for the 1500 nm trip from Kiel to the main transatlantic shipping lanes. However, as the design was refined and reality intervened, the design was upgunned, and a high-pressure steam plant was used instead of diesel engines, which were considered too novel. This reduced the cruising range by almost half, to 8525 nm, along with a substantial reduction in cruising speed, to 19 knots.
The Bismarck class was poorly suited as a commerce raider, due to their short operational range but at least they had sufficient speed to elude any pursuit. The Bismarck class' top speed was greater than any opposing British capital ship, including their largest battlecruiser Hood (due to her age) and new King George V-class battleships.
Germany, in an inferior naval position compared to Britain, could never meet the Royal Navy in a traditional battle such as Trafalgar or Jutland. Therefore, pending the completion of Grand Admiral Erich Raeder's "Plan Z" (designed to built a fleet that could fight the British on equal terms), the existing battleships, including Bismarck and Tirpitz, were to be used for hit-and-run raids.
The Bismarck class, with its design compromises, was intended merely as an interim design that would eventually be supplemented in the German main battle line by a larger and more capable design, the H class battleship. Raeder had in mind ships in the 60,000 ton category, armed with eight guns, but the outbreak of war—and the subsequent tertiary status given the Kriegsmarine compared to the rest of the Wehrmacht—prevented any of these grandiose schemes from coming to pass.
The basic layout of the horizontal protection was more questionable, in light of lessons learned in World War I, particularly at Jutland. This had emphasised that multiple thin layers of horizontal armour were less effective than a single thick layer. This vulnerability was accentuated in long-range plunging fire. Postwar tests by the United States Navy showed that the Bismarck's main armoured deck was penetrable at any distance greater than 11,000 metres by the USN's / 45 caliber gun. However, the magazines and propulsion plant were far better protected (immune to a range of 25,000 m). The dual armoured decks were chosen by the Kriegsmarine to guarantee that shells and bombs burst upon contact with the upper armoured deck, rather than penetrating deeper into the ship's vitals.. The main armour deck angled down to support the lower edge of belt, as originally proposed by White in 1880; however, this has the effect of forming a shell trap, which had been identified as a dangerous feature in WW1 battleships. Thus, the Bismarck class's protective arrangements provided extensive close-range protection, while leaving the ship more exposed to plunging fire.
The main fire control system was located above the (comparatively thin) main armour deck of the vessel. This made it more vulnerable to shellfire from large and intermediate calibre guns than comparable British and American vessels. British and American capital ships mounted their main fire control systems underneath the main armour deck. This was proved all too true in the Bismarck's final battle, when the main fire control was knocked out of action early in the fight. This again was a known problem: the two armoured decks and the belt tended to constrain and intensify explosions.
The main battery turrets were reasonably well-protected, but armour thicknesses were less than those of contemporary British (King George V) and French (Richelieu) designs. Conversely, the secondary battery was better-protected than most rivals.
Another anachronistic design feature was a 145 mm belt of citadel armour, rising from the top of the main armour belt to the main deck. This was a contradiction of the all-or-nothing principle adapted by British and American battleships; the practice of citadel armour was only mirrored in the Italian Vittorio Venetos. The weight of this armour could have been used for thicker deck armour instead. The citadel armour concept was retained by the Germans due to their concerns over close-quarters battle with British cruisers and destroyers in confined seas, such as the North Sea.
The underwater protection system was built around a single torpedo bulkhead of 45 millimetres thickness, coupled to an outboard void space; no bulges were fitted. This system was design to prevent critical damage from a 250 kg torpedo warhead. A multiple-bulkhead system, a staple of US capital ship design, could not be accommodated on the Bismarck class because of beam restrictions. The depth of the system was further limited by the change from turboelectric drive to steam turbines, which necessitated bulkier machinery. However, the propulsion plant was extensively sub-divided, such that a serious hit would still disable only two of the ship's boilers.
Immune zone analysis of the armour scheme shows that it was inferior to that of all RN battleships built from 1920 onwards. The good points were that the Bismarck class had a very broad beam (if not broad enough to fit a multiple bulkhead torpedo protection system), making it very stable as a gunnery platform and making it, together with the extensive subdivision of the ship, very torpedo resistant, in part. In the final mission and battle half a dozen torpedo hits against the main armour belt were absorbed virtually without causing any damage, except for the single hit which damaged the rudder. In the final battle only four heavy shells penetrated the armour belt (two through the upper citadel and two through the lower thicker main belt) and none penetrated the main armour deck. This was mainly due the fact that the duel was fought at medium and short ranges.
The third survey of the wreck of the Bismarck found no underwater penetrations of the ship's fully-armoured citadel and only four direct hit holes on it above the waterline, all of them on one side, as delivered by the Rodney's 16-inch (406 mm) guns. Huge dents showed that the 14-inch (356 mm) shells fired by the King George V bounced off the Wotan-type German belt armour.
The American expedition estimated that Bismarck could still float for at least a day when the British vessels ceased fire and could have been captured by the Royal Navy. They concluded the direct cause of sinking was due to scuttling: sabotage of engine-room valves by her crew, as claimed by German survivors.
In all 2,876 shells of various calibres were fired by the British ships. Approximately 300–400 hit. Only two hits fully penetrating the main armour were located. These holes were on the starboard side, suggesting that they were 16-inch shells from Rodney. Two other penetrations were found on the port side, above the main armour belt, and appeared to be by 14-inch shells. In all 714 14-inch and 16-inch shells were fired by the two battleships, of which about 80 hit the Bismarck. In successive hits main gun shells destroyed or silenced A turret, B turret, each of the three directors, D turret, C turret and the conning tower/ bridge.
An additional flaw is the choice of only three screws instead of a more common four as in most American, British, and Japanese battleships of the time. The central shaft of the three-screw setup compromises the strength of the keel particularly where it emerges from the hull. A four-screw setup allows greater flexibility and maneuverability. It would have also allowed the Bismarck more effective steering "by propeller revolutions" after her rudder was disabled by a torpedo. However, the triple-screw arrangement required a lesser beam (an important consideration, given the constraints of the Kiel Canal) and left space for the torpedo-protection system.
The problems in steering Bismarck with propellers alone became obvious during her Baltic sea trials. The rudders were locked in a neutral position and an attempt was made to steer with differential power on the propellers. The propellers' effect was minimal. This may have been due to the port and starboard propeller shafts being aligned along converging lines with the center shaft, which would have reduced their capacity to turn the ship by asymmetrical thrust. No thought was given during trials to seeing what would happen if the rudders were locked hard over. This would have grave repercussions for Bismarck during its only combat mission.
This disproportion between firepower and overall tonnage is due in part to the Bismarcks use of four twin turrets (the 4 × 2 configuration), a design practice that harkened back to the First World War. Almost all other post-1921 capital ships had triple or even quadruple turrets, which allowed for additional heavy calibre guns, while reducing the number of turrets. Although triple turrets were considered for the Bismarcks, there were concerns that the extra barrel would lower the overall rate of fire in each turret, along with fears that a single well-aimed hit could disable a larger proportion of the ship's firepower. It was also felt that four twin turrets allowed for a better field of fire and a more effective sequence of salvoes. Therefore, twin turrets were retained.
The Iowa class represented a later design than the Bismarck class, being a post-Washington Treaty fast battleship design whereas the Bismarck was treaty-limited to an extent. The earlier North Carolina and South Dakota ships were also Treaty-restricted but were slower and had a lower displacement, while their guns had a heavier broadside but shorter range.
Additionally, the Germans had experience with 38-cm naval guns; a 40.6-cm weapon would have had to have been designed from scratch. The Bismarck was also authorized prior to the breakdown of the London Naval Treaty and the invocation of the 45,000-ton, 406-mm main gun escalator clause; building 40.6-cm battleships would doubtless have seemed provocative, especially to the United Kingdom. As it was, the 38-cm main battery of the Bismarck class compared well to their contemporaries, outranging almost all of the 380-mm and 406-mm guns of contemporary navies (with the exception of the Italian 381-mm gun, which suffered exceptional bore erosion as a consequence). The German gun was superior to the World War I era BL 15 inch /42 naval gun (381 mm) of the Royal Navy in both range and penetration.
An innovation of the US Navy and Royal Navy was that they combined the secondary battery with the heavy anti-aircraft guns, creating a dual-purpose secondary battery. They discarded the dedicated, anti-ship secondary batteries altogether, because a battle-line fleet would be screened against cruiser and destroyers most of the time. Also, it was deemed unlikely that a battleship would be simultaneously facing both rushing destroyers and aircraft, and it would take up too much space to have separate types of guns to deal with both threats. Rather, the British and Americans replaced them with turret-mounted dual purpose guns that could be used against both aircraft and ships. The space saved from combining the two types of guns added to simplification of supply, increased deck armour coverage, stowage of other equipment, a larger light anti-aircraft battery, and other needs. For example, a Royal Navy battleship of the King George V class had sixteen guns that could engage either enemy ships or high level aircraft, as necessary. This arrangement was far more efficient, and was deemed adequate to meet anti-surface and anti-aircraft needs under most circumstances.
The Kriegsmarine, in a practice similar to the other Axis navies (as well as the Soviet fleets), adopted a mixed-calibre secondary battery, with dedicated anti-ship guns, coupled with smaller-calibre heavy anti-aircraft batteries, instead of adopting dual-purpose secondaries like the British or Americans. The French Navy used a mixed-calibre system, as well, but their secondary battery was dual-purpose, as per Royal Navy/USN practice. This tended to complicate ammunition supplies and render certain armament useless in some situations.
The Bismarck had a battery of twelve cannons that were designed to be used against ships only. The Kriegsmarine supplied time-fused shrapnel shells for these guns to put up a long-range curtain of fire against approaching bombers. They were useless against high-flying fast bombers and torpedo bombers skimming the surface. They could not be elevated sufficiently and, at six rounds per minute, fired too slowly to be effective. Sixteen weapons were mounted to counter aerial threats. In order to accommodate both sets of guns, the numbers of both guns had to be compromised, reducing the anti-ship and anti-aircraft broadside. A serious flaw was that the ships' designers did not give each gun mount its own fire director. This meant that when fire-direction instructions were relayed, the forward C31 gun fired at the target, and the aft C37 gun fired at a point behind the target..
While a dual-purpose, single-calibre secondary battery was considered by the Kriegsmarine, it was not adopted. When the Bismarcks were designed, the Germans did not have a 128-mm range weapon with the requisite hitting power, range, and rate of fire to adequately defend the ship. Moreover, the Germans were particularly concerned about the large numbers of heavy destroyers used by the Royal Navy at the time, and concluded that a larger-calibre secondary battery was a necessity, so as to disable attacking destroyers in the shortest possible time. However, even when a 128-mm weapon and mount more suitable to dual-purpose work was developed, it was never incorporated into later German capital ship designs, even in the final paper design, the H-44 class.
The light anti-aircraft battery consisted of two weapons. Sixteen 3.7-cm guns were distributed in twin, stabilized mounts. With a much greater rate of fire (30–40 shots/minute) than the 10.5-cm heavy AA battery, the 3.7 cm were designed to provide medium-range defense to a maximum range of 6,750 metres. The smallest weapons were the 2.0-cm (20 mm) autocannons. Bismarck carried twenty of these in two quadruple and twelve single mounts. After the ship sank, the Germans decided to augment the AA battery on the Tirpitz, and additional 20 mm were specified for their ease of installation; first 50, then 78 eventually were fitted in Tirpitz by 1944. This augmentation was typical of most navies during the war, although several (especially the Japanese) took pains to augment the heavy AA battery as well.
The flak-direction center, based on the revolving ring system, was mounted on a 40-ton revolving base. When engaged against hostile aircraft, the movement of this unit tended to affect the ship's stability. Most importantly, the base was extremely sensitive to underwater hits. The slightest damage could cause the ring to break, resulting in a total system breakdown. Through a curious oversight in the design of the Bismarck's AA gun directors, obsolescent Fairey Swordfish biplanes were able to penetrate its heavy flak screens and deliver torpedo attacks without casualty. This was due to the aiming devices not being built to allow for such slow flying aircraft; the lead sights had been designed assuming the enemy would deploy faster, newer aircraft. The Bismarck's AA guns also could not depress sufficiently to hit the low-flying Swordfish.