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Iranian frigate sunk by US submarine in Indian Ocean
The Iranian warship Iris Dena, which had recently participated in an Indian-led naval exercise, was torpedoed by a US submarine off Sri Lanka's coast on 4 March, killing at least 87 sailors. The incident has raised questions about India's regional influence and the expanding scope of the US-Iran conflict.
From diplomatic guest to wartime casualty
Just two weeks before its destruction, the Iris Dena had been a guest of the Indian Navy in Visakhapatnam, a port city on India's eastern seaboard. The frigate, part of Iran's Southern Fleet, joined 73 other nations and 18 warships for the International Fleet Review 2026 and Exercise Milan, a multilateral naval event aimed at showcasing India's maritime leadership.
Photographs from the event captured the ship's arrival, with Iranian sailors in crisp uniforms and the vessel gliding into the harbor under clear skies. Social media posts from the Indian Navy celebrated "Bridges of Friendship" and "United Through Oceans."
Retired Vice Admiral Arun Kumar Singh, who attended the exercise, recalled seeing the Iranian crew during a parade. "I saw the boys marching in front of me," he said. "All young people. I feel very sad."
The attack and its aftermath
The Iris Dena, a Moudge-class frigate commissioned in 2021, was operating approximately 20 nautical miles west of Galle, Sri Lanka, in waters under Colombo's search-and-rescue jurisdiction when it was struck. According to US Defense Secretary Pete Hegseth, the vessel "thought it was safe in international waters" but "died a quiet death."
Singh, a former submarine commander, said the attack likely involved a single Mark-48 torpedo, a heavyweight weapon capable of splitting a ship in two. The frigate sank within minutes, leaving little time for rescue. Sri Lankan authorities recovered 87 bodies, while 32 sailors survived after an SOS was picked up by Colombo's Maritime Rescue Coordination Centre.
The Indian Navy later deployed aircraft and ships to assist in the search, though Singh noted that submarines rarely surface to aid in rescues, as doing so would expose their position.
India's diplomatic dilemma
The sinking has placed India in an awkward position. While Delhi has strengthened defense ties with Washington, it also maintains long-standing political and economic relations with Tehran. Prime Minister Narendra Modi has called for "dialogue and diplomacy" to resolve conflicts but has not directly addressed the incident or criticized the US strike.
Iran's Foreign Minister Abbas Araghchi condemned the attack as "an atrocity at sea," emphasizing that the frigate had been "a guest of India's Navy." Meanwhile, Sri Lanka took control of another Iranian naval vessel after it experienced engine failure and sought port a day after the attack.
India's External Affairs Minister S. Jaishankar spoke with Araghchi by phone and met Iran's Deputy Foreign Minister Saeed Khatibzadeh in Delhi, but India's official response has remained cautious.
Strategic fallout and unanswered questions
The incident has sparked debate within India's strategic community. Brahma Chellaney, a prominent analyst, described the sinking as a "strategic embarrassment" for Delhi, arguing that Washington had turned India's "maritime neighborhood into a war zone."
"By sinking a vessel returning from an Indian-hosted multilateral exercise, Washington effectively turned India's maritime neighbourhood into a war zone, raising uncomfortable questions about India's authority in its own backyard."
Brahma Chellaney, strategic affairs expert
Kanwal Sibal, a former diplomat, suggested that while India bore no legal responsibility, it had a moral obligation to acknowledge the loss of life among its invitees. Others, like military historian Srinath Raghavan, noted that the incident highlighted the "spreading geography of this war" and India's limited ability to manage its consequences.
Unanswered questions remain: Why was the Iris Dena still near Sri Lanka nearly a week after the exercise? Was it returning home or on another mission? How long had the US submarine been tracking it?
Singh speculated that the US, which tracks vessels globally, would have known the ship's movements. Analysts estimate that a quarter of America's 65-70 submarines are at sea at any given time.
A war at India's doorstep
For India, the episode underscores the challenges of balancing relationships with rival powers. As Raghavan put it, the US Navy's actions sent a message to all regional players, including Delhi: "The war has come to our doorsteps. That is not a good thing."
