The Wreck of DKM Bismarck − A Marine Forensics Analysis 1 The ...

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The Wreck of DKM Bismarck − A Marine Forensics Analysis SOME OBSERVATIONS Bismarck's sinking was a brutal, up-close action. Admiral Tovey wanted to sink Bismarck with the gunfire at his disposal. Swordfish aircraft with torpedoes were in the vicinity but were not called upon to enter the action. Point-blank fire was relatively ineffective, with many shells skipping off the water and riddling the superstructure pointlessly, or missing entirely because of the low freeboard. At short ranges, the salvo dispersion pattern was narrower and more elongated. Since both British battleships were firing almost straight abeam Bismarck, on either side, they were trying to hit a target with very little freeboard in a high sea state. These miserable conditions − violent seas and marginal visibility − made good gunnery accuracy an “iffy” prospect, at best. Unless the shells hit below the armor belt, very unlikely at such close ranges because of protective effect of water with such flat trajectories, they were not going to cause damage that would sink the ship. As a result of the port list, by the end of the gunnery engagement, the lower edge of the armor belt on the port side may have been submerged some 7-8 meters below the water (perhaps two deck heights) − much more than normal. In a sense, the port list contributed to protecting the port side of the damaged ship from gunfire, every degree of added list decreasing the vulnerability of many vital compartments. By 0945; it was becoming obvious that British shellfire was not contributing to sinking the ship. The two battleships and two heavy cruisers had fired away for the last hour without any apparent effect. Shellfire had riddled the stack structure, swept away searchlights, demolished the antiaircraft batteries, pummeled the superstructure, carried away hose reels and fire extinguishers, and destroyed the teak deck in areas. Crew members who were in exposed areas were killed or severely wounded. Close-range gunnery later in the engagement devastated Bismarck’s superstructure and the parts of the hull structure above the waterline, overwhelming and defeating the ship and causing massive casualties, but not speeding the sinking of the ship. Bismarck was overwhelmed and defeated by the gunfire and torpedoes of the Royal Navy, gradually sinking due to uncontrollable progressive flooding. Scuttling charges were detonated shortly after 1020, and the battered ship listed heavily to port around 1035. Shortly thereafter, the ship capsized to port and sank by the stern, her bow disappearing around 1040. THE WRECK The hulk of Bismarck is lying upright, with its bow facing West across the slope of an extinct volcano on a heading between 250-290°. The bow-first impact caused an enormous disturbance to the terrain, including an impact crater where the bow first hit, and an impact trough where the hull slammed down moments later, both of which are surrounded by ejecta. The hull immediately slid South down the seamount stern first, gouging a deep slide scar which widened as the hull turned broadside to the slope and continued to slide at a slight bow-first angle. In this broadside area the slide scar is shallower and more chaotic. Down slope, beyond the wreck, there is a huge alluvial fan of sediment and debris. The wreck caused a terrestrial avalanche on the seabed which was exacerbated by a powerful turbidity flow. During her plunge through the water column, Bismarck planed north, transiting about 500 meters horizontally to the North from her sinking position on the surface. She struck the side of a 34
The Wreck of DKM Bismarck − A Marine Forensics Analysis seamount (extinct volcano) and subsequently slid down its slope for a distance of 1,000 meters. During that slide, she passed directly across Ground Zero (directly beneath the epicenter of the sinking where Bismarck left the surface.) This is significant, because heavier debris, such as the four main battery turrets, fell more directly to the seafloor without planning, which put them in the path of the ship as it slid downhill. Bismarck slid through part of her own debris field. This caused the displacement of Turret Bruno and the forward command tower and the burial of other parts of the ship that had fallen into the sea during the capsizing process. Bismarck slid one kilometer down the slope, accompanied and partially propelled by a powerful turbidity flow and avanlanche of disturbed sediment. The avalanche/turbidity flow was induced by the impact and slide of the ship, and also by the continued downward flow of the entrained water flow-field created above the ship as it sank through the water column. The four main battery turrets landed upside down with their gunhouses buried in the sediment, and their substructures exposed in varying degrees. Minutes later the sliding hull came through the debris field, missing Turrets Caesar and Dora, which lie only meters west of the slide scar, but impacting Turrets Anton and Bruno. Turret Bruno was pushed downhill and came to rest approximately 200 meters south of Bismarck’s bow. This turret can be identified by the fact that the rear of the turret is missing, as had been reported by Seaman Josef Statz to author William Garzke. The gunnery reports of both Rodney and King George V attest to heavy damage to this turret during the course of the battle on 27 May. The other three turrets are located about 350 meters north of the wreck, two just west of the slide scar and what is probably Turret Anton just inside the scar, to the east. Anton shows clear evidence that the ship actually slid right over it, removing the turret’s substructure and jamming it into a rock outcropping, leaving behind a large piece of red bottom shell plating wrapped around the turret. Extrapolating Turret Bruno north to its original impact position yields a clear pattern. All four turrets landed in an east-west line, in the same order and spacing as they were on the ship. Very little planning took place on descent, despite a fall of 5,000 meters through the water column. From this the ship’s heading and position at the exact moment she capsized can actually be confirmed. The main hull is upright with no discernible list or trim. Examination of the hull revealed that there was not any visible longitudinal bending of the hull. There is some localized buckling of the hull and armor plates abeam the Turret Bruno barbette, particularly on the starboard side. This buckling was likely caused at the first moment of impact, as the bending moment pushed the bow up relative to the longitudinal axis of the ship. Moments later, as the ship settled, this bending moment reversed itself, leaving a buckled region but no permanent bending of the hull. This same effect is prominently visible at the Titanic wreck. The upper citadel (145 mm) and lower (320 mm) main side belts show evidence of shell hits, with two penetrations in each. The decks and remaining superstructure are covered with rubble and fine-particle sediment that was stirred up during the hull’s slide and subsequent settlement. All six 150-mm secondary turrets remain in their barbettes, with all their guns in place. Turret 62 34 has the back portion of its 80-mm armor roof missing. All secondary turrets exhibit shell hits from 134-, 152-, and 203-mm shells. Some of these are non-penetrating hits, but there 34 The 150-mm (about 6-inch) secondary turrets have been identified in this paper by a two-digit number, such as 62. The “6” denotes the gun caliber, while the second number locates the turret. Odd numbers are to starboard and even ones are port locations, with the lower numbers being forward. 35
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