Tuesday, July 16, 2024

HMS Hood ‘sunk by mechanical failure, not Bismarck’

It was the most shocking loss of a Royal Navy warship in the Second World War, and may have been completely misunderstood. HMS Hood did not sink due to a “lucky hit” from the German battleship Bismarck, but as a result of catastrophic metal fatigue, a new paper suggests.

The British battlecruiser, which had been the world’s largest warship for over 20 years, sank only six minutes into the Battle of the Denmark Strait in the early morning of May 24, 1941. All but three of the 1,418 men on board perished. The New York Times‘ Washington Correspondent wrote: “The gravity of the blow to British naval supremacy could be measured here by the stunned silence with which the news of the Hood was received [. . .]”

The action unfolded in rough seas in the strait between Greenland and Iceland when Hood, along with the battleship Prince of Wales, sought to prevent Bismarck and the heavy cruiser Prinz Eugen breaking out into the North Atlantic to prey on Allied merchant shipping.

The British battlecruiser HMS Hood at anchor early in the Second World War. Photo: Imperial War Museum, © IWM HU 76082

The official narrative, established after two wartime boards of inquiry, concluded that the First World War vintage Hood was destroyed due to a lucky hit on one of its magazines by a shell from the 1939 ship Bismarck. This had been the thinking in the immediate aftermath, when a Press Association correspondent wrote that “a well-directed salvo from the Bismarck must have scored a direct hit on a vulnerable spot — almost a million-to-one chance.”

According to Martin Lawrence, author of the research paper presented to the Royal Institution of Naval Architects, the chances of such a hit were indeed vanishingly small. Explaining the genesis of his study, he said: “My background is in mathematical physics and I have worked in industry all my life, here and in America. When I was at school, I developed an interest in the Royal Navy and its ships and what they did — I just picked up books and read them. And over the years, partly from my professional background, the interest stayed. I became focused on Hood after talking with a colleague. The story about the way she met her end just didn’t add up.”

Now, following 12 years of part-time research, he argues that a neglected firsthand account of the sinking by one of Hood‘s survivors is the key to reinterpreting the evidence and understanding what may have happened.

In the Admiralty’s reconstruction, the fatal shell was part of the fifth salvo fired by Bismarck and struck Hood somewhere between its rearmost funnel and mainmast. The shell penetrated deep into the ship, over 70ft, before starting a fire in one of its magazines. This became a raging inferno within seconds, sending a tall column of flames shooting into the air close to the mainmast before causing the rest of the magazine to explode, to catastrophic effect. This seemed reminiscent of the losses of the battlecruisers IndefatigableQueen Mary and Invincible at the Battle of Jutland in 1916 — all due to magazine explosions following shell hits.

The 1939 German battleship Bismarck firing at HMS Hood during the action in the Denmark Strait. This photograph was taken from the German heavy cruiser Prinz Eugen. Photo: Imperial War Museum, © IWM HU 381

Even at the time of the inquiries, Sir Stanley Goodall, Director of Naval Construction, expressed doubts, however. Goodall, then considered the world’s foremost authority on warship design, referred to the lucky hit theory as only “the probable cause”. Likewise, in his 1950s official history of the Royal Navy during the Second World War, Captain Stephen Roskill wrote that “the exact cause of the loss [of Hood] will never be known for certain.”

Among the problems with the lucky hit theory highlighted by Goodall was that it required the shell to have exploded considerably further into the ship than would be expected with a typical fuse. In fact, Goodall said the shell that supposedly hit Hood would have needed a fuse delay two to three times longer than that of a shell from Bismarck found unexploded in Prince of Wales.

Even more difficult to explain is how, if a 15in shell exploded in one of Hood‘s magazines, this didn’t cause an instantaneous sympathetic detonation of all the cordite present. In any case, given the relative positions of the ships, Lawrence argues that shells from Bismarck would have struck Hood at such low angles as to make any penetration of the ship unlikely.

Furthermore, Captain John Leach, commanding Prince of Wales, recalled that the column of fire appeared within a couple of seconds of Bismarck‘s salvo. Lawrence said: “That infers a fire of quite colossal intensity and a fire of that extent is not going to start, build up and find a route 60 feet forward in two, three or four seconds. That really was the hardest part to imagine.”

Able Seaman Robert Tilburn, of Leeds, one of the three survivors of HMS Hood, with his young brother, June 1941. Photo: Imperial War Museum, © IWM HU 50191

He believes the true explanation has been hiding in plain sight — in eyewitness testimony from Able Seaman Robert Tilburn that was given at the second inquiry and effectively ignored. Tilburn, a Yorkshireman who was 20 years old at the time of the sinking, said that “after Bismark’s second salvo fell [close to Hood but not hitting] the vessel was shaking with a great vibration.”

According to Lawrence, the only way that a ship as large as Hood‘s 48,000 tons could be made to shake like this was through a serious fault in its propulsion system. In his analysis, this most likely involved a propellor shaft breaking out of its bearing mounts and windmilling about until it broke. In his paper, he writes: “There is just nothing else on the ship with sufficient power to do this and there is no reason for Tilburn to make this up; in the disaster that was about to unfold around him, this was something unusual enough that he specifically remembered it.”

Crucially, Hood‘s inner propellor shafts passed within five feet of the main magazines at the rear of the ship, with their 112 tons of explosive cordite. Lawrence continues: “Each of her four propeller shafts was responsible for pushing some 12,000 tons of Hood along, in a storm, at 28 knots; a quite immense amount of power. Any breakage of these shafts or their bearing mounts, themselves of heavy and solid construction, would cause large and quite massive metal pieces, probably hot from explosively disintegrating, to go flying about. These parts would easily have enough energy to smash through local steel walls and with the magazines so close it is inevitable that these would be penetrated in a shower of red hot sparks.”

In Lawrence’s analysis, these sparks would likely have set alight bags of cordite, causing a fire that spread rapidly. At the same time, the flailing propellor shaft would have reamed open the bulkhead between the engine room and the magazines and shaft tunnels at the rear of the ship. Fire and smoke would have been drawn through the engine room, exiting by the main ventilation trunk near the mainmast — the exact position of the column of flames observed from Prince of Wales.

At this point, Hood would have been doomed, but most of the crew would have had no idea of what was happening and Lawrence believes that efforts to return fire on Bismarck hastened the British ship’s end. Specifically, reloading the guns in one of two stern turrets that were seen to fire, would have involved opening anti-flash doors. This would have allowed far more air to flow into the magazines, then out through the hole in the engine room bulkhead and up via the ventilation system to leave the ship.

Such a fire tunnel would lead to further acceleration of the blaze and, only seconds later, to the explosion of the whole stock of cordite, almost vaporising a large section of the ship.

HMS Hood going into action against the German battleship Bismarck and battlecruiser Prinz Eugen on May 24, 1941. This image taken from HMS Prince of Wales was the last ever taken of Hood. Photo: Imperial War Museum, © IWM HU 50190

Lawrence said the whole sequence of events would have taken between 90 to 120 seconds from the damage occurring after Bismarck‘s second salvo to the vessel exploding — compared to the Admiralty’s timescale of a couple of seconds between the shell hit and the column of flames and a few more seconds before the explosion.

According to Lawrence, the break in the propulsion system was most likely caused by a part failing to due metal fatigue. As he writes: “Metal fatigue is insidious and can be extremely hard to detect until it is too late.” The immediate triggers could have been the enormous strain the ship was under during the pursuit and combat, the shock wave from a near miss in the sea by a German shell, or a combination of the two. Thermal factors may also have played apart, with the propellor shaft mounts close to both the hot engine room and the very cold Atlantic water.

Ultimately, however, metal fatigue would have resulted from the ship’s poor condition, which Lawrence said was abundantly documented. At the time of the battle, Hood — under construction from 1916, launched in 1918 and commissioned in 1920 — was arguably barely seaworthy. A refit that was planned for 1939 had been postponed by the outbreak of war and the ship was affectionately referred to as the fleet’s “largest submarine”. Hood not only leaked in all but the calmest seas but was visibly rusty. The condensers — a crucial part of the propulsion system — required urgent repairs after a very near miss by a German bomb in September 1939 and some other components were repaired, but not replaced, in the spring of 1940.

Most significantly, one of Hood‘s turbines partially failed following the attack on the French fleet at Mers-el-Kébir in July 1940.

In Lawrence’s analysis, six dockyard visits for heavy repairs during the two years before the sinking amounted to “patching up” rather than thorough overhauls. He said: “Hood‘s machinery was 20 years old and much of it was known to be in a severely worn state. Not only this, but the hull itself had required patching and re-riveting in three dockyard visits. This brings into question the security of the footings — the points at which this heavy, powerful, but elderly, machinery was fixed into the ship’s frame and exactly how secure it was.

“Given the wear and tear, some corrosion of parts, then the hammering explosions nearby of Bismarck‘s shells, a train of events can be envisaged where one of the bearing mounts supporting the propellor shaft fails and the unsupported shaft initially sags but, as it is being driven by the turbine, flails about, causing the heavy vibration reported to the inquiry. In flailing, it penetrates the magazine walls and starts the fire that ultimately condemns Hood.”

Men of HMS Hood receive training in gunnery and ammunition handling in 1940. Photo: Imperial War Museum, © IWM A 178

He believes it is especially surprising that the boards of inquiry didn’t consider mechanical failure as a possible cause of the loss, given that, in 1939, the First Sea Lord, Sir Dudley Pound, was recorded as saying: “The likelihood of her (Hood) being able to steam at high speed for any length of time was considered remote.”

The dash to intercept Bismarck took 50 hours, with Hood travelling at 25 knots or more into increasingly rough seas. Pound may well have been more prescient than he knew. Lawrence points out that, during her last hours, Hood was being driven to the very limit, both in reaching Bismarck and in manoeuvring to engage — so much so that even the new Prince of Wales could hardly keep pace. The 20-year-old machinery on board Hood was being worked flat out.

In not considering mechanical failure, was the Admiralty deliberately covering up? Lawrence doesn’t think so. He said: “I just don’t think they thought about it. I think they wanted to come to the conclusion that matched Jutland, rather than Hood. I think that clouded their thinking and they became very myopic. They had lost Hood and within four or five hours people at the Admiralty were talking about a repeat of Jutland — that suggestion fixed itself in their heads.”

The German battleship Bismarck was hunted down after Hood’s sinking. Photo: Deutsches Bundesarchiv, under licence CC BY-SA 3.0 DE

Today’s naval experts are more open-minded, according to Lawrence. He said: “When I presented my paper in Newcastle, I had three letters from retired Royal Navy officers — two rear admirals and an engineering commander — saying they knew that the HoodBismarck theory was wrong and thanking me for putting forward this alternative explanation.”

He said that another factor inadvertently influencing the navy’s original findings may have had to do with honour. “That outcome suited the psyche. Hood was a warship built to go into battle against His Majesty’s enemies and was lost in combat. So there was kind of glory to it as well. I think that also affected the thinking. But it doesn’t really match up with what people saw.”

Given the old idea that Bismarck sank Hood, the British ship was considered to have been avenged on 26-27 May when Bismarck was crippled by sustained Royal Navy attacks in the Atlantic and scuttled. If Lawrence is right, the whole story is just as tragic but less neatly resolved.

So why is it important to revisit all this, more than 80 years after the event. Lawrence said: “There’s a lot of supposition made because this sinking happened in history and ‘history repeats itself’. But it just doesn’t. What I set out to consider was the operational situation in its entirety and that included the mechanical condition of HMS Hood. Having been involved in metal fatigue and metallurgy quite a lot in my working life, once you take into account Hood‘s recent record of heavy repairs and the age and worn down condition of her machinery then ask whether metal fatigue might have played a part in the loss, lo and behold, the scales fall from your eyes.

“As Roskill pointed out, we will never know for certain what caused the loss of Hood, but it was widely known among the senior naval officers of the day that she needed fully rebuilding. The Admiralty should have included the possibility of metal fatigue in their deliberations.”

The illustration at the top of the article is a painting by German war artist Julius Schmitz-Westerholt, depicting Hood’s loss in the engagement with Bismarck on May 24, 1941. HMS Prince of Wales is in the foreground. Photo: public domain, via US Naval Historical Center / Wikimedia Commons

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