At least 80 people were killed after a US submarine sank an Iranian warship in the Indian Ocean, news agency Reuters said today. The warship, IRIS Dena, had participated in a naval exercise in India just weeks ago.
IRIS Dena, a Moudge class frigate, also came to India in 2024 to participate in the multilateral naval exercise MILAN, the same exercise’s 2026 edition from where it sailed home today when the US submarine attacked it.
While the US has not confirmed the number of dead, Defence Secretary Pete Hegseth confirmed the submarine strike and touted it as evidence of America’s global reach in its war on Iran.
“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.
The US Department of War released a black and white video of what looked like a submarine periscope and an explosion in the distance. It is unprecedented for any military to release near realtime visuals of a submarine kill. This shows the manner in which wars are fought and information is shared have seen massive changes.
https://t.co/PiqQpVIrMu pic.twitter.com/Wc1e0B0um7
— Department of War 🇺🇸 (@DeptofWar) March 4, 2026
The Iranian warship likely did not detect the US submarine even in periscope depth, which spoke a lot about the capabilities of the American submarine’s tactics.
The Indian Navy in a statement on February 16 had said that as one of the largest multilateral naval exercises in the Indo-Pacific, MILAN 2026 would bring together navies from across the globe to strengthen interoperability, maritime domain awareness, and collective response capabilities.
The harbour and sea phases of the exercise focussed on complex maritime operations including anti-submarine warfare, air defence, search and rescue, etc.
Nothing is known whether the US submarine had been tailing or observing the Iranian warship as it came to India to participate in MILAN 2026. Defence analysts have theorised that the US submarine may have been tracking the Iranian warship throughout its journey from Iran to India to participate in the exercise. It is common for navies to passively track others for intelligence gathering.
Sri Lankan authorities said they had rescued 32 crew members from the frigate IRIS Dena, but that 148 other sailors were missing, with hopes low that any more would be found.
Hegseth called the attack “quiet death” and the first US sinking of an enemy ship by torpedo since World War II. “Like in that war,” he said, “we are fighting to win.”
The Pentagon says one of the main aims of the US-Israeli war against Iran, launched Saturday, is to wipe out the country’s navy.