By Trendsetter Tribune 
In a dramatic expansion of the current conflict, a United States Navy fast-attack submarine torpedoed and sank the Iranian frigate IRIS Dena on Wednesday, March 4, 2026. The engagement took place in the Indian Ocean off the coast of Sri Lanka, marking the first time a U.S. submarine has sunk an enemy warship with a torpedo since World War II.
Details of the Engagement
- Location: The strike occurred approximately 25 miles south of the port city of Galle, Sri Lanka, in international waters.
- The Target: The IRIS Dena, one of Iran’s newest and most advanced frigates, was returning from the “Milan” naval exercises hosted by India in the Bay of Bengal.
- Casualties: Sri Lankan authorities reported that at least 87 bodies have been recovered. Of the estimated 180 crew members on board, only 32 survivors have been rescued so far.
- The Weapon: The Pentagon confirmed the use of a Mark 48 heavyweight torpedo, which reportedly broke the ship’s keel, causing it to sink rapidly.
“Quiet Death”: The Pentagon’s Response
U.S. Defense Secretary Pete Hegseth confirmed the sinking during a press briefing, characterizing the submarine’s stealthy approach as a “quiet death.”
“An American submarine sunk an Iranian warship that thought it was safe in international waters. Instead, it was sunk by a torpedo… Like in [World War II], we are fighting to win.” — Pete Hegseth, Secretary of Defense
General Dan Caine, Chairman of the Joint Chiefs of Staff, called the operation a “historic milestone” for the U.S. Navy’s submarine force.
Global Conflict Spillover
The sinking of the IRIS Dena signals that Operation Epic Fury—initially focused on the Persian Gulf and Levant—has now spread thousands of miles beyond the Middle East.
- NATO Involvement: In another significant escalation, NATO air defenses reportedly destroyed an Iranian ballistic missile over Turkey on Wednesday, the first time a NATO ally has been directly targeted in this conflict.
- Regional Anxiety: Sri Lanka’s government expressed concern over the proximity of the strike to its shores, while India—which had hosted the Dena just days prior—has remained largely silent as it monitors the threat to Indian Ocean shipping lanes.
- Naval Toll: U.S. Central Command (CENTCOM) claims that over 20 Iranian vessels have been destroyed since the war began on February 28, effectively neutralizing Iran’s “blue-water” naval capabilities.