IRIS Dena Sunk: US Submarine Fires Mark 48 Torpedo in First Kill Since World War II
A U.S. Navy fast-attack submarine has torpedoed and sunk the Iranian frigate IRIS Dena in the Indian Ocean off the coast of Sri Lanka — the first time an American submarine has destroyed an enemy warship using a torpedo since World War II. The strike is one of the most significant naval combat events in decades, and it happened on March 4, 2026, as Operation Epic Fury entered its fifth day.
IRIS Dena Sunk: What Happened off Sri Lanka
The Iranian frigate IRIS Dena was torpedoed and sunk by an American submarine in the Indian Ocean on March 4, 2026, approximately 40 nautical miles south of Galle, Sri Lanka. The U.S. Department of Defense confirmed the attack was carried out using a Mark 48 torpedo.
The ship sank at 5:08 a.m. local time after transmitting a distress call reporting an explosion, going down before Sri Lankan rescue forces could reach the location. Approximately 180 people were on board.
Sri Lanka's navy recovered at least 87 bodies and rescued 32 sailors, who were transported to Karapitiya Teaching Hospital in Galle for treatment. Rescue and recovery operations are still ongoing.
The Mark 48 Torpedo: One Shot, One Kill
Chairman of the Joint Chiefs of Staff Gen. Dan Caine confirmed at a Pentagon briefing: "For the first time since 1945, a United States Navy fast attack submarine has sunk an enemy combatant ship using a single Mark 48 torpedo to achieve immediate effect, sending the warship to the bottom of the sea. This is an incredible demonstration of America's global reach. To hunt, find and kill an out-of-area deployer is something that only the United States can do at this type of scale."
The Mark 48's roughly 650-pound warhead is designed to detonate below the waterline, powerful enough to lift a warship and cause its hull to buckle or break entirely. Pentagon footage released to social media showed the torpedo striking beneath the stern of IRIS Dena, raising the vessel off the water before it sank.
Hegseth: "Quiet Death"
Defense Secretary Pete Hegseth confirmed the strike at a Pentagon press briefing: "Yesterday, in the Indian Ocean, an American submarine sunk an Iranian warship that thought it was safe in international waters. Instead, it was sunk by a torpedo. Quiet death. The first sinking of an enemy ship by a torpedo since World War II. Like in that war, back when we were still the War Department. We are fighting to win."
Hegseth also confirmed a second Iranian warship, the Soleimani — a corvette-class missile ship — was sunk in the Strait of Hormuz near Iranian shores in a separate action.
A Historic First: Only the Second SSN Combat Kill in History
The sinking of IRIS Dena is only the second time in history a nuclear-powered attack submarine has destroyed an enemy vessel in combat — and the first ever SSN kill achieved with a guided torpedo. The last submarine to sink a warship in combat was the Royal Navy's HMS Conqueror, which destroyed the Argentine cruiser ARA General Belgrano during the Falklands War in 1982.
Whether the submarine that fired the torpedo belonged to 5th Fleet or 7th Fleet, the Pentagon has not confirmed. The identity and assignment of U.S. submarines on active operations are among the most tightly held pieces of information in the American military.
IRIS Dena: What the Ship Was
IRIS Dena was a Moudge-class frigate displacing approximately 1,300 to 1,500 tons and armed with four Qader anti-ship missiles, Sayyad air-defense missiles, a 76mm main gun, lightweight torpedoes, and a 3D phased array radar. The ship could also carry a helicopter.
IRIS Dena had recently participated in the multinational naval exercise MILAN 2026 and the International Fleet Review at Visakhapatnam, India, and was transiting home through international waters when the strike occurred.
Iranian Navy: 20+ Ships Destroyed Since Saturday
Caine told reporters that the U.S. has now sunk more than 20 Iranian naval vessels, one Iranian submarine, and the IRIS Dena since Operation Epic Fury began Saturday. CENTCOM commander Adm. Brad Cooper stated bluntly: "Today there is not a single Iranian ship underway in the Arabian Gulf, Strait of Hormuz or Gulf of Oman — and we will not stop."
The broader conflict has killed more than 1,000 people in Iran and dozens in Lebanon, while six American troops were killed in a fatal drone strike in Kuwait. Thousands of U.S. citizens remain stranded across the Middle East as the State Department urges all Americans to depart more than 14 countries immediately.
