HMS Venturer (P68): The Only Submarine to Sink Another While Both Were Submerged

Built at Barrow

HMS Venturer was built by Vickers Armstrong at Barrow-in-Furness, launched in May 1943 and commissioned on 19 August 1943, a V-class submarine that spent much of her war patrolling the Norwegian coast, watching for U-boats and coastal traffic moving in and out of German-held bases.

She made thirteen war patrols, working out of Lerwick in Shetland and Dundee, which is about as bleak a beat as the Royal Navy had. The Norwegian coast in winter means darkness for most of the day, weather that comes in without warning off the Atlantic, and a shoreline of islands, rocks and fjords that a submarine has to work close inshore because that is where the traffic hugs the coast.

The V class she belonged to was small, which was the point. She was a coastal boat of a few hundred tons, developed from the U class, and a small submarine is easier to hide in shallow water and easier to turn in a fjord. What she did not have was much of anything else: modest speed, a limited battery, and a hydrophone set as her only way of hearing anything at all when she was deep.

A Solid Wartime Record

Beyond the engagement for which she is best remembered, Venturer sank three Axis vessels during 1944, including the German submarine U-771 on 11 November 1944 near the Lofoten Islands, and accounted for five merchant ships off the Norwegian coast during her operational career, a remarkably productive record even before her most famous action.

There is a second distinction in there that the tally does not draw out. Venturer sank two U-boats, and the published records note that she was the only British or German submarine of the entire Second World War to do it. Britain put a couple of hundred submarines to sea in that war and Germany more than a thousand, and one small V-class boat with one captain accounted for two of the other side's.

The first was U-771, on 11 November 1944 in the Andfjord about seven miles east of Andenes, and it is worth having the detail because it shows exactly what the famous action was not. At thirty-nine minutes past eight in the morning Venturer sighted a conning tower at three thousand five hundred yards, on the surface, making fifteen knots. At quarter to nine she fired four torpedoes from two thousand yards. At forty-six and a half minutes past there was an explosion, then the crackling noise of a hull breaking up, and by ten to nine there was nothing in the periscope.

That is a normal submarine attack against a normal target: something visible, on the surface, with a course and speed that can be seen and measured. Nearly every U-boat sunk by a British submarine in the war was killed exactly like that. HMS Tuna sank U-644 that way, HMS Satyr sank U-987, and HMS Tally-Ho caught UIT-23 the same way in the Malacca Strait. What happened three months later was a different thing entirely.

An Unrepeated Feat of Naval Warfare

On 9 February 1945, under her 25-year-old commanding officer Lieutenant Jimmy Launders, Venturer detected the German Type IX U-boat U-864 by hydrophone near Fedje Island off the Norwegian coast.

Launders tracked his target for some three hours while submerged, and facing depleted batteries, made the extraordinary decision to compute a firing solution entirely by hand, a technique that had never been attempted before because the calculations required to hit a three-dimensionally manoeuvring target were assumed to be practically impossible.

Why the Sum Was Considered Unsolvable

The difficulty is worth setting out, because it is a specific mathematical problem rather than general difficulty. A torpedo attack requires the target's course, speed and range, and the ordinary way to get all three is to look at it: a periscope gives a bearing and, from the apparent size of a known type of ship, a range, and repeated looks give a course and speed.

Venturer could not look at anything. U-864 was submerged, so all Launders had was a hydrophone bearing, which is a direction and nothing else. No range, no depth, no idea of the target's aspect. And U-864 was zigzagging, so the bearing kept changing for two reasons at once, the target turning and both boats moving.

Solving that means manoeuvring your own submarine deliberately so that the way the bearing changes tells you something, and doing the geometry in your head and on paper while it happens. Launders did it for about three hours, in a boat whose battery was steadily going flat, knowing that if he ever had to surface to charge he would be a stationary target for a submarine that had been listening to him for just as long.

The spread of four at seventeen-second intervals is the answer to the last unknown. He could not know the target's depth, so he did not try to. He laid a wall of torpedoes across where U-864 had to be and let her steer into one, which she did, having evaded the first three by turning.

At 12:12, he fired all four bow torpedoes at staggered 17-second intervals and depths; U-864 evaded the first three, but unknowingly steered directly into the path of the fourth. The German boat exploded, split in two and sank with the loss of all 73 men aboard, some 31 nautical miles from Bergen.

The sinking remains, to this day, the only occasion in the history of naval warfare on which one submarine has sunk another while both were submerged, the only naval engagement ever fought entirely underwater.

The claim is worth stating precisely, because it is often repeated loosely and then attacked. Submarines have sunk other submarines many times. What has happened only once is both of them being submerged at the moment of the attack, with the whole engagement conducted by one boat against another with no part of either above water and no help from anybody else.

It has not happened since, and it is very unlikely to happen the way Venturer did it. Modern submarines carry sonar that gives ranges as well as bearings and fire-control computers that do in a second what Launders did in three hours. The feat that will not be repeated is not the sinking, it is the arithmetic.

Launders was awarded a bar to his DSO for the action, and his manually computed firing solution went on to establish techniques that influenced modern torpedo targeting systems. U-864 had been on a clandestine mission to Japan under Operation Caesar, carrying 65 tonnes of mercury and components for the Junkers Jumo 004 jet engine, adding a further layer of strategic significance to an already extraordinary action.

That cargo is still there, and it has become somebody else's problem. U-864 was found in 2003 by the Norwegian Navy, in two pieces, a couple of miles off Fedje in around 150 metres of water. The mercury was stowed in steel flasks in her keel, and after sixty years the flasks had begun to corrode.

Mercury does not break down. It settles into the seabed, gets into shellfish and works its way up the food chain, and the seabed around the wreck is now measurably contaminated over a wide area. Norway has been arguing about what to do since the day it was found. Raising the wreck risks breaking the remaining flasks; covering it means accepting that a large quantity of a toxic metal stays on the seabed off a populated coast indefinitely.

The decision went to covering. Work to cap the site with sand and rock began in 2018, ran a long way past its original schedule, and as recently as 2024 the government was looking again at whether some of the mercury could be recovered after all. It is not a settled matter, and anybody who tells you it is finished should be asked which year they are describing.

The tonnage is given variously as sixty-four, sixty-five and sixty-seven, which is the sort of discrepancy you get when the manifest is a German wartime document and the cargo is at the bottom of the sea. All three figures describe the same thing: more mercury than anybody has a safe use for.

A Second Life in Norway

HMS Venturer was sold to the Royal Norwegian Navy in 1946 and renamed Utstein, serving under the Norwegian flag until January 1964, when she was struck from their register and subsequently scrapped, a fitting final posting for a submarine whose most famous action had taken place in Norwegian waters.

There is a neatness to it that is easy to miss. The submarine that killed U-864 off the Norwegian coast spent the next eighteen years serving the Norwegians, under a Norwegian name, in the same water. She was one of several British boats handed over to rebuild a navy that had spent the war in exile.

Launders was twenty-five when he made the attack and had been in command since the day she commissioned. He received a bar to his Distinguished Service Order for it, which is a decent award and, set against what he had actually done, a slightly muted one. The Royal Navy has never been quite sure what to do with a feat that consists mostly of somebody thinking very clearly for three hours.

The name is back in the fleet. A new Venturer, the first of the Type 31 frigates, is coming into service, and her ship's company marked the eightieth anniversary of the action in February 2025.