OPINION | Beyond the Exercise: India's Case for Non-Responsibility in the IRIS Dena Incident
- 2 days ago
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by Ashu Mann
In the early morning hours of March 4, 2026, the Iranian frigate IRIS Dena was torpedoed and sunk by a U.S. submarine approximately 40 nautical miles off the southern coast of Sri Lanka, near the city of Galle. The vessel transmitted a distress call at 0508 hours local time before sinking, prior to Sri Lankan rescue forces reaching the area. There were approximately 180 people on board. At least 87 individuals were killed, and 32 survivors were rescued and transported to Karapitiya Teaching Hospital in Galle.
U.S. Defense Secretary Pete Hegseth confirmed the strike during a Pentagon briefing, describing it as the first American submarine sinking of an enemy vessel since World War II. The attack was part of Operation Epic Fury, a joint U.S.-Israeli military campaign against Iran that had begun days earlier.
IRIS Dena had participated in India's multilateral MILAN naval exercise. In the days following the attack, a wave of commentary questioned India's naval responsibility, a claim that several defense and naval officials have since firmly rejected.
The sea phase of the MILAN exercise formally concluded on February 24, 2026. From the afternoon of February 25 onward, participating vessels departed the Visakhapatnam coast. According to a senior retired naval officer, the status of visiting ships changes once they leave Indian waters.
"The moment a vessel leaves Indian shores, it ceases to be our guest and our responsibility," the officer explained. "India's maritime obligations extend to its territorial waters, not to a ship's entire onward journey home."
IRIS Dena's last port of call after departing India was Hambantota, Sri Lanka. Following that stop, the vessel was observed operating in international waters for more than eight days. Three days after the MILAN exercise concluded, the United States and Israel began military operations against Iran, with U.S. strikes recorded on the morning of February 28, 2026.
The location where IRIS Dena was ultimately attacked falls under the jurisdiction of the Maritime Rescue Coordination Centre (MRCC) Colombo. Sri Lankan authorities responded in accordance with international maritime procedures. After learning of the incident, the Indian Navy activated its assets to support potential search and rescue efforts.
"The Indian Navy's obligation in such a scenario is limited to search and rescue, and only when requested," the veteran officer added. "That request never came through Indian channels. What happened in international waters, during an active conflict between other nations, falls outside our jurisdiction."
Questions have also been raised about IRIS Dena's extended presence in the region after leaving Visakhapatnam. Some observers have suggested that the vessel's eight-day loitering period in international waters may have reflected Iran's own operational planning in relation to U.S. naval forces rather than any connection to the MILAN exercise. Given the ongoing hostilities, the United States could have regarded IRIS Dena as a belligerent vessel and therefore a legitimate target regardless of location.
History offers several precedents. In 1915, the British liner RMS Lusitania was struck by a German torpedo in the open Atlantic, not in a defined war zone or contested territorial waters but in the middle of the ocean. Nearly three decades later, in October 1941, the American destroyer USS Reuben James met a similar fate when it was sunk by a German submarine in the North Atlantic, months before the United States had formally entered World War II. In both cases, the ocean provided no immunity. Once conflict begins, it rarely respects the invisible maritime boundaries between nations.
More than twenty Iranian vessels have reportedly been struck by U.S. forces during the ongoing conflict, yet the sinking of IRIS Dena has attracted disproportionate international attention.
A pointed counterargument has also emerged. Had IRIS Dena launched an offensive strike against U.S. assets during that same eight-day window, would the narrative then suggest that an Indian multilateral exercise had effectively served as the launch platform for an Iranian naval operation?
About the Author
Ashu Mann is an Associate Fellow at the Centre for Land Warfare Studies. He was awarded the Vice Chief of the Army Staff Commendation card on Army Day 2025. He is pursuing a PhD from Amity University, Noida, in Defence and Strategic Studies. His research focuses include the India-China territorial dispute, great power rivalry, and Chinese foreign policy.