Galle (TDI): In the early hours on Wednesday, the Iranian frigate IRIS Dena sent out a distress call from international waters roughly 40 nautical miles off the southern coast of Sri Lanka. The ship had approximately 180 crew members on board. It sank before rescue teams could reach it.
The cause was a single Mark 48 torpedo fired from a United States Navy fast-attack submarine. The Pentagon confirmed the strike the same day.
Defense Secretary Pete Hegseth called it a “quiet death” at a press briefing, the first sinking of an enemy warship by an American submarine since World War II.
Sri Lankan authorities recovered at least 87 bodies and rescued 32 survivors, who were taken to Karapitiya Teaching Hospital in Galle for treatment. Over 100 crew members remain missing.
The IRIS Dena was one of Iran’s most advanced warships. A Moudge-class frigate commissioned in 2021, it was armed with anti-ship missiles, surface-to-air missiles, torpedoes, and a 76mm naval gun.
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It had the capacity to carry a helicopter and was equipped with a radar system capable of tracking targets across a 300-kilometer range.
The ship had just completed participation in the International Fleet Review and the MILAN 2026 naval exercises in Visakhapatnam, India, and was on its way back to Iran when it was struck.
Its sister ships, IRIS Jamaran and IRIS Sahand, have already been destroyed in earlier US strikes during Operation Epic Fury. So has Iran’s drone carrier, the IRIS Shahid Bagheri.
The sinking of the Dena is significant because it makes only the second time in history that a nuclear-powered submarine has destroyed an enemy vessel in combat.
The first was in 1982, when Britain’s HMS Conqueror sank the Argentine cruiser ARA General Belgrano during the Falklands War.
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It is also the first time a guided torpedo has ever been used to achieve a submarine kill. Chairman of the Joint Chiefs, General Dan Caine, confirmed these details at the Pentagon and said US forces have now destroyed more than 20 Iranian naval vessels since the operation began.
The location of the strike is as significant as the strike itself. The operation is spearheaded by US Central Command, with naval forces based in the Arabian Sea and surrounding waterways.
The Dena sunk hundreds of miles to the east, in the Indian Ocean, well within US 7th Fleet territory. That means the conflict has now expanded geographically beyond the Middle East and into the Indo-Pacific.
How Iran responds to the sinking of the Dena will define what comes next in a war that is showing no signs of de-escalation as of now.
