U.S. Submarine Torpedoes Iranian Frigate in Indian Ocean in First Wartime Strike of its Kind Since World War II

An Iranian Navy warship has been sunk by a U.S. Navy attack submarine in the Indian Ocean, marking what U.S. officials say is the first time since World War II that an American submarine has destroyed an enemy warship with a torpedo.

The vessel, identified as the IRIS Dena, a Moudge-class frigate operated by the Islamic Republic of Iran Navy, was struck by a U.S. Mk-48 heavyweight torpedo approximately 40 to 44 nautical miles south of Galle, Sri Lanka, according to multiple media reports and officials. The ship sank following the strike.

U.S. Central Command said Wednesday that American forces have struck or sunk more than 20 Iranian vessels since hostilities with Tehran escalated late last week.

The Department of War shared video footage of the strike along with images of the ship sinking on social media:

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

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

The attack represents a dramatic escalation in the maritime dimension of the rapidly expanding conflict between the United States, Israel, and Iran, which began when U.S. and Israeli forces launched coordinated strikes against Iranian targets over the weekend.

In a post on X, the U.S. Department of War framed the attack in historic terms. “In the Indian Ocean—an American submarine sunk an Iranian warship that thought it was safe in international waters,” it said. “Instead, it was sunk by a torpedo—Quiet Death. The first sinking of an enemy ship by a torpedo since World War II.”

According to reports carried by several international outlets, the Dena was carrying approximately 180 crew members at the time of the attack. Sri Lankan authorities said search-and-rescue units recovered 32 survivors from the water, while dozens of sailors are believed to have been killed or remain missing.

The strike occurred as the Iranian frigate was reportedly transiting westward through the Indian Ocean after participating in the multinational MILAN naval exercise hosted by India.

The attack comes amid an intensifying maritime security crisis across the Middle East shipping lanes. Since Sunday, the Joint Maritime Information Center has raised the regional threat level to “critical” following a concentrated wave of missile and drone attacks targeting commercial vessels near the Strait of Hormuz and Gulf of Oman.

The widening naval confrontation has already triggered a dramatic pullback in marine insurance coverage for ships operating in the Gulf while tanker traffic through the Strait of Hormuz has reportedly collapsed by roughly 90% as shipowners reassess the risk of operating in the region.

U.S. officials have not publicly identified the submarine involved in the attack, and the Pentagon has not yet released operational details about the engagement.

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