80 feared dead as US submarine sinks Iranian warship in Indian Ocean

The warship, a Moudge-class frigate operated by the Iranian Navy, had participated in the multilateral naval exercise MILAN 2026 in India just weeks ago.

It had also taken part in the 2024 edition of the same exercise before sailing back toward Iran when it was struck.

While Washington has not officially confirmed the death toll, US Defence Secretary Pete Hegseth acknowledged the strike, describing it as a demonstration of American naval reach.

“An American submarine sunk an Iranian warship that thought it was safe in international waters. Instead, it was sunk by a torpedo,” Hegseth told reporters, calling it a “quiet death” and the first US sinking of an enemy vessel by torpedo since World War II.

The United States Department of Defense released black-and-white footage appearing to show a submarine periscope view followed by a distant explosion, an unusual move given the traditionally secretive nature of submarine warfare.

Analysts say the near real-time release of visuals underscores how modern conflicts are increasingly fought not only on battlefields and at sea, but also in the information domain.

Sri Lankan authorities said 32 crew members from IRIS Dena had been rescued, while 148 sailors remained missing, with hopes fading for additional survivors.

Defence analysts noted that the Iranian frigate likely did not detect the American submarine, even if it had been operating at periscope depth, a sign, they say, of the stealth and tactical superiority of US undersea capabilities.

It remains unclear whether the submarine had been tailing the vessel since it departed India after MILAN 2026. Naval experts point out that passive tracking of foreign warships for intelligence purposes is common practice among major maritime powers.

Exercise in focus

In a February 16 statement, the Indian Navy described MILAN 2026 as one of the largest multilateral naval exercises in the Indo-Pacific, aimed at strengthening interoperability, maritime domain awareness and collective response capabilities.

The harbour and sea phases of the drill included complex operations such as anti-submarine warfare, air defence manoeuvres and search-and-rescue missions.

The Pentagon has said one of the primary objectives of the US-Israeli military campaign against Iran is to neutralise Tehran’s naval power, raising concerns of further confrontations in the region’s strategic waterways.

The sinking of IRIS Dena signals a significant shift in the maritime dimension of the conflict — and potentially a dangerous widening of hostilities across the Indian Ocean.