The General Belgrano left port from Tierra del Fuego on April 26th, 1982, with Task Force 79.3 consisting of two destroyers - the ARA Piedra Buena (D-29) and the Bouchard (D-26). Both vessels were also ex-American World War 2-era warships. The purpose of the sortie was to counter the British task force that was reported heading south to land more troops in the islands. The Argentine military decided to counter this and reinforce the islands with more Argentine troops in turn. As part of these maneuvers, the Belgrano and her task force, along with the aircraft carrier ARA Veinticinco de Mayo, was ordered to take positions around the islands.
By April 29th, the ships were patrolling the Burdwood Bank south of the islands. On the 30th, the Belgrano was detected by the British nuclear-powered fleet submarine HMS Conqueror. The submarine shadowed the cruiser over the following days and requested permission to fire. After consultation at the British Cabinet level, the decision was made that the Belgrano proved a definitive threat to British shipping and Conqueror should proceed to attack the Belgrano. On May 2nd, Conqueror closed in and fired three conventional Mk 8 mod 4 torpedoes, each with a 800lb (363 kg) Torpex warhead. Two hit the Belgrano - the first striking foward at the bow with the internal bulkheads holding. As such, the forward powder magazine did not detonate.
The second torpedo exploded behind the second smoke stack outside the coverage of the side armor plating, exploding in the rear machine room. The explosion blew through heavily trafficked areas before killing some 275 sailors, revealing a sixty foot long hole in the main deck. While the explosion did not set off an onboard fire, the resulting detonation produced heavy smoke which limited communications and rescue. Furthermore, the vessel began to take in water while her electrical system was damaged, restricting any communications to be sent to the destroyer screen for assistance. During the chaos, the Conqueror quietly retired to a safe position to observe.
Having taken on water, the Belgrano then began to list to port and sink by the head. Just twenty minutes after the attack, Captain Bonzo of the Belgrano ordered the abandon ship. While orderly, the evacuation was complicated by the increasingly uneven seas.
The two escort destroyers were unaware of the sinking due to the lack of a distress call and went about their business laying depth charges. When it was finally revealed that the Belgrano was badly damaged and in need of assistance, night had fallen and the sea swells rose, making rescue of the crew in rafts a dangerous affair. It was not until May 5th that all the crew were rescued by a combined Argentine-Chilean endeavor and some 770 men were located and brought aboard. The attack on the Belgrano had claimed 321 of her personnel.
After a land engagement, Argentina formally surrendered control of the islands to the UK on June 14th, 1982 but showed no sign of relinquishing her political claims to the islands (a stance continued to this day). In 1994, the Argentine government and Captain Bonzo indicated the sinking of the Belgrano was a legal act under the rules of engagement of the day.