US Submarine Sinks Iranian Frigate in Indian Ocean

New Delhi, March 5, 2026: In a significant escalation of the ongoing regional conflict, the United States Pentagon has confirmed that a U.S. Navy fast-attack submarine torpedoed and sank the Iranian frigate IRIS Dena in the Indian Ocean. This incident, occurring on March 3, 2026, represents the first time an American submarine has destroyed an enemy vessel with a torpedo since the end of World War II.

The Incident: A “Quiet Death” in International Waters

U.S. Defense Secretary Pete Hegseth officially confirmed the strike during a Pentagon briefing, describing the operation as a “quiet death.” According to the Pentagon, the IRIS Dena—a Moudge-class frigate and a pride of the Iranian Navy—was struck by a single Mark 48 heavyweight torpedo while transiting international waters south of Sri Lanka.

The strike was part of the broader “Operation Epic Fury,“ a campaign aimed at degrading Iran’s naval and military capabilities.

Key Details of the Strike:

• Target: IRIS Dena (Moudge-class frigate)
• Location: Approximately 20 to 40 nautical miles south of Galle, Sri Lanka.
• Weapon Used: A single Mark 48 ADCAP (Advanced Capability) torpedo.
• Casualties: Sri Lankan authorities and reports confirm at least 87 sailors killed.
• Survivors: The Sri Lankan Navy rescued 32 crew members following a dawn distress call.

Strategic Context: Returning from India

The timing of the attack has raised diplomatic eyebrows across South Asia. The IRIS Dena was on its return voyage to Iran after participating in the International Fleet Review (IFR) 2026 and the Exercise MILAN in Visakhapatnam, India. These multinational exercises, hosted by the Indian Navy, included participants from over 70 countries—ironically, including assets from the United States.

The fact that the vessel was targeted so shortly after a diplomatic maritime event highlights the total breakdown of traditional “rules of engagement” in the current conflict.

Historical Significance

Military historians and analysts have noted the rarity of this engagement.

1. First Since 1945: This is the first combat kill by a U.S. submarine using a torpedo since the sinking of Japanese vessels in World War II.
2. SSN Combat Success: It marks only the second time in history that a nuclear-powered attack submarine (SSN) has sunk an enemy ship in combat (the first being the HMS Conqueror sinking the General Belgrano during the 1982 Falklands War).

Regional Impact and International Reaction

The strike has brought the West Asian conflict directly into the Indian Ocean, a zone typically characterized by heavy commercial shipping and strategic stability.

• Sri Lanka: The Sri Lankan government has emphasized its commitment to humanitarian obligations, focusing on the search and rescue of the remaining missing crew (estimated at over 60 people).
• India: While the Indian government has not issued an official condemnation, analysts suggest the proximity of the strike to Indian waters is a cause for “deep concern” regarding the safety of regional maritime routes.
• Iran: The Iranian Revolutionary Guard Corps (IRGC) has vowed “complete destruction” of regional military infrastructure in retaliation, signaling that the conflict may move toward vital energy corridors like the Strait of Hormuz.

Current Status

Search and rescue operations are ongoing off the coast of Galle. Meanwhile, the Pentagon has released black-and-white footage of the strike, showing the devastating impact of the torpedo on the frigate’s hull. Defense Secretary Hegseth reiterated the U.S. stance: “We are fighting to win.”