U.S. Navy Submarine Torpedoes Iranian Frigate In Indian Ocean

A U.S. Navy attack submarine has sunk an Iranian warship in the Indian Ocean, the Pentagon has confirmed. Authorities in Sri Lanka had earlier announced they had rescued Iranian sailors from the Moudge class frigate IRIS Dena after what they said appeared to be a submarine attack. This is the first known attack by an American submarine on a surface warship since World War II and the first such action anywhere since the Churchill class HMS Conqueror sank the Argentine Navy cruiser ARA General Belgrano during the Falklands War in 1982.

“Yesterday in the Indian Ocean, … an American submarine sunk an Iranian warship that thought it was safe in international waters,” Secretary Pete Hegseth said at a press conference this morning. “Instead, sunk by a torpedo, quiet death, the first sinking of an enemy ship by a torpedo since World War II.”

A view of the Iranian frigate, bow up, sinking after being torpedoed by a US Navy submarine in the Indian Ocean. US Military

At the same briefing, Chairman of the Joint Chiefs of Staff U.S. Air Force Gen. Dan “Razin” Caine said the same attack had been carried out by an unspecified “fast attack submarine” using a single Mk 48 torpedo.

Authorities in Sri Lanka had earlier announced they had rescued Iranian sailors from the IRIS Dena after what they said appeared to be a submarine attack. The Sri Lankan Navy responded to a distress call from the ship, and launched rescue operations at 6:00 AM local time,  Sri Lanka’s foreign minister told ​parliament.

A stock picture of the Iranian Navy frigate IRIS Dena. (Indian Navy)

“What ​we know at this point is that 79 people were ​rescued and brought to the hospital and one of them was seriously injured. ‌Another ⁠101 are believed to be missing and the vessel has sunk,” a Sri Lankan navy source told Reuters

A ​Sri Lankan navy spokesman also said that “32 people ⁠injured in the incident had been rescued by [the] Sri Lankan ​navy and were under treatment in hospital,” Reuters explained, adding that one of those brought in had subsequently died.

Iran’s Moudge class frigates, derived from the earlier Alvand class, are among Iran’s most modern and capable surface combatants. Iranian Alvand class warships and derivatives thereof have also been targeted in port in U.S. strikes in the course of Operation Epic Fury.

Another stock picture of the IRNS Dena. (Indian Navy)

“We’ve destroyed more than 20 Iranian naval vessels, including – in addition to the frigate outside of the area,” Gen. Caine also said this morning. “[We’ve] effectively neutralized, at this point in time, Iran’s major naval presence in theater.”

“Over the next 24 to 48 hours, CENTCOM [U.S. Central Command] will continue to strike infrastructure and naval capability, and we’ll continue to assess our progress against the military objectives,” he added.

U.S. officials have previously highlighted the total destruction of Iran’s Navy as a central objective of Operation Epic Fury, an effort that is now extending beyond the Middle East.

UPDATE: 9:32 AM EST –

The Pentagon has now released a video, seen below, of the torpedo attack on the Iranian frigate in the Indian Ocean, as seen through the periscope (technically an optronics or photonics mast) on the U.S. Navy submarine. The infrared footage shows a massive detonation at the stern end of the ship.

https://t.co/PiqQpVIrMu pic.twitter.com/Wc1e0B0um7

— Department of War 🇺🇸 (@DeptofWar) March 4, 2026

Modern heavyweight anti-ship torpedoes like the Mk 48 are designed to cause maximum damage after striking the target ship well below the waterline. The Mk 48 torpedo’s roughly 650-pound warhead is powerful enough to ‘lift’ a warship and cause its hull to buckle, if not break entirely, as is regularly seen in U.S. Navy sinking exercises.

You can read more about how modern submarines execute torpedo attacks, which are nothing like how they are depicted in movies and television, in a past TWZ feature here.

Contact the author: howard@thewarzone.com

Howard Altman Avatar

Howard Altman

Senior Staff Writer

Howard is a Senior Staff Writer for The War Zone, and a former Senior Managing Editor for Military Times. Prior to this, he covered military affairs for the Tampa Bay Times as a Senior Writer. Howard's work has appeared in various publications including Yahoo News, RealClearDefense, and Air Force Times.

Joseph has been a member of The War Zone team since early 2017. Prior to that, he was an Associate Editor at War Is Boring, and his byline has appeared in other publications, including Small Arms Review, Small Arms Defense Journal, Reuters, We Are the Mighty, and Task & Purpose.