HMS Conqueror (S48): The Only Nuclear Submarine to Sink a Warship in Combat

The Build: Birkenhead

HMS Conqueror was built by Cammell Laird at Birkenhead, laid down on 5 December 1967 and launched on 28 August 1969, though construction was delayed by workforce disputes and even sabotage of the ship's gearbox.

That is a startling thing to pass over in four words. Sabotage on a nuclear submarine under construction is not vandalism, it is an attack on a warship, and a damaged main gearbox on a submarine is a very serious matter indeed: the gearbox is what turns the turbine's output into shaft revolutions, it is buried deep inside the hull, and a fault in it produces exactly the noise a submarine exists to avoid making.

It also has to be said that no culprit was ever produced and no motive was ever established, which is why the incident is usually mentioned and then dropped. Cammell Laird in the late sixties was a yard with dreadful industrial relations, and a job that went from a 1967 keel to a 1971 commissioning had a great deal going wrong with it besides.

She was the last submarine Cammell Laird ever built. A yard that had been turning them out since before the First World War finished with this one.

She was commissioned on 9 November 1971, the last nuclear submarine ever built at Cammell Laird, a Churchill-class fleet submarine designed from the outset to counter the Soviet Navy, armed with six torpedo tubes capable of firing Mark 8 and Tigerfish torpedoes alongside Sub Harpoon missiles.

The Churchill class were the second generation of British nuclear submarines, and their job was singular and unglamorous: to find Soviet ballistic missile submarines and follow them, silently, for weeks, so that if a war started they could be killed before they launched. Conqueror spent the great majority of her career doing that in the Norwegian Sea and the Barents, and almost none of it can be written about. HMS Courageous and HMS Sceptre were doing the same work in the same water.

The Sinking of the General Belgrano

On 2 May 1982, during the Falklands War, Conqueror, under the command of Commander Christopher Wreford-Brown, fired three older Mark 8 torpedoes at the Argentine cruiser ARA General Belgrano from roughly 1.5 kilometres away, deliberately choosing the older weapons over more modern guided torpedoes because they were judged more effective against the cruiser's armoured hull.

Two of the three torpedoes struck home, and the Belgrano began sinking rapidly within twenty minutes.

The attack killed 323 Argentine sailors, while 793 of her crew were rescued, which remains, to this day, the single deadliest incident of the entire Falklands conflict.

Why an Old Torpedo Was the Right One

The choice of weapon is the part of the attack most often reported as a curiosity and it was a straightforward engineering decision. The Tigerfish was the modern weapon, wire-guided, clever, and designed to run out to a submarine and detonate underneath it, breaking its back with the gas bubble rather than punching a hole. It was also, in 1982, notoriously unreliable.

The Mark 8 was a design from the 1920s that ran straight and hit the target in the side with several hundred pounds of Torpex. Against General Belgrano, which had been laid down in 1935 as the American cruiser USS Phoenix and had an armoured belt and torpedo bulges built to absorb exactly that kind of hit, a straightforward contact explosion below the belt was more likely to work than a sophisticated weapon that might not run at all.

It worked. One torpedo struck forward and blew off her bow; the other hit aft of amidships, went through the armoured belt and wrecked her machinery and electrical supply, which meant no power, no pumps and no way to broadcast an abandon-ship order except by word of mouth. The order came within about half an hour and she went down not long after.

One figure in that account is settled and one is not. The 323 dead is firm and nobody disputes it. The number rescued depends on how many were aboard, and published sources give her complement as anywhere between about 1,090 and about 1,140, so survivor counts vary by several dozen. The rescue itself took two days in a Force 8 in the South Atlantic, and that Argentine ships were allowed to search unmolested is worth recording.

A Lasting Controversy

The sinking has remained a point of genuine and long-running controversy, principally because the Belgrano was outside Britain's declared Total Exclusion Zone and, according to critics, was sailing away from the Falkland Islands at the time she was struck.

It is worth knowing what else was in the water, because Conqueror was not working alone. HMS Spartan was the first British submarine on station and had been off the islands since before the landings, and other nuclear boats were spread across the approaches. Their presence is a large part of why the Argentine navy, including the carrier Veinticinco de Mayo, stayed in port for the rest of the war after 2 May.

The conventional submarine HMS Onyx came south as well, and did the inshore work the nuclear boats could not, because a nuclear submarine needs deep water and cannot sit on the bottom close to a coast.

That is the strategic argument about the Belgrano, and it is separate from the legal and political one. After 2 May the Argentine surface fleet went home and stayed there, which removed one of the two threats to the British landings at a stroke. Whether that justifies the decision is precisely the question people have been arguing about for forty years.

The British government's position rested on a message sent to Argentina on 23 April, warning that any Argentine vessel judged a threat to British forces could be engaged regardless of the exclusion zone's boundaries, a warning some senior Argentine officers later acknowledged they had understood to mean the whole South Atlantic had effectively become an operational area for both sides.

The decision to change the rules of engagement specifically to permit the attack has continued to generate debate ever since about the military and political judgement behind it, a debate this history does not attempt to settle but which deserves to be acknowledged honestly.

The Log That Went Missing

One strand of that argument turns on a document. Conqueror's control room log for the period went missing after the war and has never been produced, and for three decades that was treated by critics as evidence that something about the Belgrano attack was being concealed.

A different explanation was published in 2012 by the journalist Stuart Prebble, and it needs stating carefully because none of it has ever been officially confirmed and the operation concerned remains classified. According to that account, in August 1982, only weeks after Conqueror came home from the South Atlantic, she went to the Barents Sea on an operation codenamed Barmaid.

The target was a towed sonar array: a two-mile string of hydrophones streamed astern of a Polish intelligence-gathering vessel, and the newest Soviet submarine-detection equipment in existence. Conqueror is said to have been fitted with electrically operated cutting pincers supplied by the Americans, to have got underneath the tow, cut a three-inch steel cable, and to have taken the array home to the Clyde, from where it was flown to the United States for analysis.

The argument about the log follows from that. If Conqueror's logs covered a peacetime operation of that kind against the Soviet Union, destroying them has an explanation that has nothing to do with the Belgrano at all. Whether that is what happened is not something anybody outside the Ministry of Defence can establish, and it should be read as a competing account rather than a settled one. It is, however, a reminder that a missing document can have more than one reason for being missing.

Conqueror herself holds the distinction of being the first nuclear-powered submarine ever to sink an enemy surface ship with torpedoes in wartime, a record that stood alone for 44 years until March 2026, when a US submarine torpedoed the Iranian frigate IRIS Dena, a singular and sobering entry in naval history.

That comparison is very fresh and the particulars are worth having, along with a caution. On 4 March 2026 the United States submarine Charlotte, a Los Angeles-class boat, fired two Mark 48 torpedoes at the Iranian frigate IRIS Dena roughly nineteen nautical miles off Galle, on the southern coast of Sri Lanka, and sank her. The Dena was on passage home from an international fleet review in India.

Everything else about it is contested. The casualty figures reported vary, the question of what armament the frigate was carrying is disputed, Iran has called the attack a war crime, and there is an active argument in the United States about the legal authority for it. Anyone reading about it now is reading a first draft, and the account here will need revisiting as the record settles.

What the two events have in common is worth noticing all the same. Both were carried out by a nuclear submarine whose crew never saw the ship they sank except through instruments; both killed hundreds of men in minutes; and in both cases the argument afterwards was not about whether the attack worked but about whether it should have been made at all. Forty-four years apart, and the shape of the controversy is identical.

Decommissioning

HMS Conqueror was decommissioned in 1990, and as of 2019 remained one of more than twenty former Royal Navy nuclear submarines held in storage by the Ministry of Defence awaiting final disposal, while items from the boat are preserved at the Royal Navy Submarine Museum in Gosport.

The storage problem deserves a plain description, because it is not a filing issue. A decommissioned nuclear submarine cannot simply be scrapped. The reactor compartment is radioactive, the fuel has to come out first, and until quite recently Britain had no agreed method or site for taking the rest apart. So the boats were defuelled, sealed, and tied up afloat at Devonport and Rosyth, where they have been ever since, requiring maintenance, inspection and money.

Conqueror has now been laid up for longer than she was in commission. She was in service for nineteen years and has been waiting to be dismantled for more than thirty-five, which is an odd fate for the only British submarine since 1945 to have sunk an enemy warship.

Her Jolly Roger is at Gosport. She came home to Faslane in July 1982 flying it, and the flag she flew is the one the Royal Navy has been sewing symbols onto since 1914. There was nobody left in 1982 who had done it for real before.