US Submarine Sinks Iranian Frigate IRIS Dena with MK-48 Torpedo in Indian Ocean – First Torpedo Kill Since WWII

In a striking escalation of Operation Epic Fury, a U.S. Navy attack submarine has sunk the Iranian frigate IRIS Dena with an MK-48 heavyweight torpedo in the Indian Ocean, approximately 40 nautical miles south of Galle, Sri Lanka. The strike, confirmed by U.S. Defense Secretary Pete Hegseth, marks the first time since World War II that an American submarine has destroyed an enemy warship using a torpedo.

The MK-48, a wire-guided, acoustic-homing weapon capable of speeds over 50 knots and ranges exceeding 20 nautical miles, struck the Alvand-class frigate in international waters. Hegseth described the action as a “major blow” to Iran’s already battered naval operations, following the sinking of over 20 Iranian vessels in the Persian Gulf and Strait of Hormuz in the campaign’s opening days.

Sri Lankan authorities reported the frigate issued a distress call early March 6, 2026. The Sri Lanka Navy dispatched rescue vessels, recovering dozens of the approximately 180 crew members amid ongoing search efforts for survivors. Multiple fatalities have been confirmed, though exact numbers remain unverified.

The attack extends the U.S.-Iran conflict far beyond the Middle East, into the Indian Ocean—a critical global trade artery carrying roughly 40% of the world’s oil shipments. Iran’s navy, once a regional power with ambitions to project influence through the Bab el-Mandeb and beyond, now faces severe attrition: surface fleet losses, command disruptions from air strikes on IRGC facilities, and the loss of key assets like the Dena.

This undersea strike highlights America’s unmatched submarine dominance—Virginia- and Los Angeles-class boats operate undetected across vast distances, delivering devastating precision without risking surface assets. As B-2 bombers, PrSM missiles, and carrier strikes continue hammering Iran’s homeland, the submarine’s silent kill in distant waters signals a multi-domain campaign designed to isolate, degrade, and deter Tehran’s ability to sustain prolonged warfare.

With global energy routes at risk and allies watching nervously, the Indian Ocean incident underscores how quickly a regional conflict can spiral into a broader maritime confrontation.