What Sank the Lusitania?

by Brian Dunning
July 12, 2022

It was May 7, 1915, just off the southern coast of Ireland. The British Empire and the Allied Powers were deeply embroiled in World War I against the German Empire and the Central Powers. Germany had declared unrestricted submarine warfare, meaning their subs would sink merchant vessels without warning just as they would warships. The ocean liner RMS Lusitania, loaded with 1,962 passengers and crew, was slowing for foggy conditions just after 2pm in the afternoon. The German submarine U-20 spotted Lusitania's funnels. Finding the slow-moving ship unescorted and making no defensive maneuvers, and knowing that all such passenger liners were loaded with munitions for the Allied war effort and were thus legitimate merchant targets, a torpedo was fired. The explosion shattered the starboard side of the hull, and a mere 18 minutes later, the mighty liner descended to the bottom of the Celtic Sea, taking 1,198 souls with it.

It was a very sad chapter in maritime history, and one that could be easily put to rest if the story ended there. But it didn't. For, even though there's no doubt about the facts of the case as just given, mystery still clouds the loss of the Lusitania. For it was not the torpedo's mighty blast that sank her, according to the survivors, but a much more powerful second explosion — a second explosion for which nobody seems to be able to nail down a source.

Today, the Lusitania lies on the ocean floor in very poor condition. It's quite accessible, being just off the southern coast of Ireland in only 93m of water, well within the reach of technical divers. Considering the ship was 240m long, if stood on end the majority of the wreck would be up out of the water! It seems such a shame; if one end could be floated to the surface the ship would be at a 21° angle, little more than a steep hike for all its ghosts to walk up to safety. But the ship's hard landing and more than a century of time have not been kind to it. It landed on its starboard side, bent backward like a banana from the loss of rigidity due to its superstructure having disintegrated on its way down. Since then the wreck has collapsed and flattened, as if deflated, and is reported to be continuing to rapidly deteriorate.

Oceanographer and wreck chaser Bob Ballard made a series of dives on the Lusitania in 1993, and he reported the hull had flattened to about half its original beam, and that the wreck was a ruin of 50 years of blasting and salvaging operations. He also found its cargo of 173 tons of munitions, unexploded and undisturbed, eliminating all possibility that they could have been responsible for the second explosion. Ballard was also able to thoroughly inspect the hull's port side, which had been reported to be holed by some earlier reports, and found that it was undamaged — eliminating even more possibilities.

Normally the ability to explore a sunken ship gives us answers to questions, but the exploration on Lusitania has not lived up to that promise. And when we have a vacuum of knowledge, sometimes conspiracy theories and other alternate explanations creep in to fill the gaps. Thus, we see the inevitable result: wild hypotheses abound to explain what sank the Lusitania. Let us now discuss a few of these, beginning with a good old fashioned conspiracy theory:

Did Winston Churchill engineer a conspiracy?

During World War I, future Prime Minister Winston Churchill was the First Lord of the Admiralty, essentially the top administrator of the United Kingdom's naval forces. It has been suggested — often passionately — that Churchill allowed the sinking to happen, perhaps by ordering Captain Turner to cruise in a leisurely, easy-target fashion, in order to enrage Americans and thus get the United States to enter the war on the Allied side.

The only piece of evidence anyone's ever found in support of this is a letter Churchill once sent to Britain's Board of Trade:

It is most important to attract neutral shipping to our shores in the hope especially of embroiling the United States with Germany... For our part we want the traffic — the more the better; and if some of it gets into trouble, better still.

The whole notion is silly, of course — in no small part because the Lusitania was not that "neutral shipping" Churchill referred to. He was talking about American ships, as the United States was the most significant neutral country. But Lusitania was British, not American — it would be no skin off the Americans' nose if the Germans sank it. If Churchill had been of a mind to engineer a false flag attack to pull the Americans into the war, an American ship is what he would have needed to sink — not one of his own.

Was there one torpedo or two?

The question of how many torpedos were fired depends on who you ask, and when you asked them. For a time in the aftermath of the sinking, everyone on the Allied side believed there had been been two torpedos: one striking between the bridge and the first funnel, the second striking between the third and fourth funnels. An 18-year-old lookout up on the bow shouted into a megaphone "Torpedoes coming on the starboard side!", believing he'd seen two parallel bubble trails coming toward the ship.

But otherwise, all the other sources say there was but a single torpedo fired. Aboard the U-20 submarine, the captain, the torpedo officer, the crew, and the boat's log all say a single torpedo was fired. Even their radio report made of the sinking, which was intercepted by the Allies, stated a single torpedo was used — and this report was made before any hypothetical reason to falsify it would have arisen. The U-20 only had three torpedos left, and each was precious; a second would not have been fired if it hadn't been needed. The captain said he couldn't have fired a second one anyway because of the danger to all of the people in the water; but you can choose to take that with a grain of salt. The fact remains that all the documentary evidence shows a single torpedo was fired, and nobody has ever suggested a rational reason that they'd want to falsify and cover up the number of torpedos used.

You can suggest "Oh, the captain would have been charged with war crimes if he saw people in the water and fired a second torpedo anyway," but if he had taken the time to observe the effects of the first torpedo and then fired a second, the explosions would have been separated by minutes, not by seconds.

Was there actually a second explosion?

Pretty much everyone agrees there were two explosions — the only problem with this being that no source for a second explosion has ever been proven, and most possible sources for a second explosion have been ruled out. There is no film or audio recording or any evidence that would tell us how many explosions there were, so we can rely only upon eyewitness testimony.

The U-20's torpedo officer, who was the one watching through the periscope, reported that the torpedo's explosion was unusually large (and that's what the captain recorded in the log), but of course they couldn't hear anything. So we have ambiguous and inconclusive evidence from them.

But of the survivors from the Lusitania, including the captain himself, every person among them said there were two explosions, a few seconds apart. Lacking any data or evidence to the contrary, we should take this as the null hypothesis. So unless more information is forthcoming, we can say for now that yes, there were indeed two explosions.

If there was a second explosion, what was it?

So we've already knocked out two possibilities: it was not a second torpedo, and it was not the cargo of munitions. Strictly speaking, the ammunition on board was not even classified as "munitions" as it was mainly cartridges for Remington .303 rifles, plus some empty 76mm shell casings, and non-explosive fuses. The rifle cartridges are not explosive and wouldn't cause an explosion even if hit directly by a torpedo.

Eliminating these two leaves us with a handful of other possibilities. But before you go researching this on your own, a word of warning: Virtually every headline you'll see reads something like "New evidence" or "Fresh revelations" or "New discoveries"... well, no. None of these headlines are true. All the possible causes have been bandied about since the very beginning, and no evidence has ever surfaced giving any of them any real support. Always remember: with every old mystery come constant claims of new solutions. In almost all cases, such claims are false.

1. A coal explosion

Bob Ballard favored the coal explosion hypothesis, persuaded by having found coal all over the seabed around the wreck. When the torpedo struck, it could have knocked a huge amount of coal dust into the air, producing a highly explosive cloud that could have been easily ignited from sparks or the boilers or any of a number of sources.

There are two reasons nearly everyone else dismisses this hypothesis. First, the coal in ship bunkers was notoriously damp from being in contact with the condensation on the hull, too damp to ever really produce any dust. Second, there were survivors from all the boiler rooms, and none of them reported that the second explosion had come from there. So it's plausible, but in this case, nearly impossible to shoehorn in.

2. A boiler explosion

Boilers typically did explode when steamships like the Lusitania sank, but usually only after they were flooded in the sinking. The sudden influx of cold water would greatly increase the pressure, and the hot boilers would explode. This did happen as the Lusitania went down, but again, we know it did not happen initially because of the reports from survivors from all the boiler rooms.

3. An unknown supply of explosives

Was Lusitania secretly also carrying explosives that could have gone up as a result of the torpedo? It would seem improbable. There was no hesitation about properly listing munitions on the manifest; in fact, doing so was essential for the proper supply of the war effort. Beyond that, inspection of the wreck has revealed no evidence of internal explosions, and anything like that would have been obvious to all the survivors — none of whom reported it.

4. A steam line explosion

In addition to high-pressure boilers, steamships had high-pressure lines from the boilers to the engines, and other places. Could one of these have exploded, producing the deafening second explosion sound that everyone heard? Certainly it could have, but note that bursting steam lines might not necessarily cause all that much damage other than to the pipe itself, depending on where the rupture was.

And this opens us up to a pretty big question:

Was a second explosion necessary to sink the ship?

The consensus seems to be no, that the damage from the one torpedo was enough to sink the Lusitania regardless of any second explosion. Comparisons with the Titanic are inevitable, and while the Titanic had watertight bulkheads that were quite large and that only failed due to the unforeseen extent of the iceberg damage, Lusitania's were smaller and considered deficient by modern naval architects. The location of the torpedo strike produced catastrophic flooding in the starboard coal bunker of boiler room #1, and the longitudinal bulkheads caused this to result in a starboard list severe enough that the water was easily able to overflow the starboard ends of the lateral bulkheads — just as happened on the Titanic. Whether a second explosion caused additional damage or not may have impacted the speed with which Lusitania sank, but she was going down no matter what. The lone torpedo from the U-20 had sealed her fate.

So, was there a second explosion? Probably. Whatever made that loud bang remains unknown, but it may or may not have been destructive, and may or may not have contributed to the speed of the sinking. It's a mystery that doesn't matter, like what caused your car engine to stall after the car had already jumped off the cliff. It could be one of the possibilities we just discussed; it could have been one of the others we didn't go into like unfounded rumors of bombs on board; it could have been something nobody's ever thought of. But one thing is a virtual certainty: it's almost guaranteed to remain a mystery, as the evidence just doesn't exist. So of any headlines announcing the explanation has finally been found, you should continue to be skeptical.

By Brian Dunning
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