The United States has confirmed it used a submarine‑launched torpedo to sink an Iranian warship in the Indian Ocean. Defence Secretary Pete Hegseth told reporters on Wednesday 4 March that a US Navy attack boat struck the IRIS Dena late on Tuesday. Sri Lanka’s authorities, who first received the distress call, said 87 bodies had been recovered and 32 sailors rescued, with around 180 believed to have been on board. The incident occurred roughly 40 nautical miles south of Galle, in international waters. (washingtonpost.com)
Sri Lanka’s foreign minister Vijitha Herath told Parliament that the distress signal arrived at 05:08 local time on Wednesday and that Colombo launched a joint navy–air force response. Officials stressed the site lay outside Sri Lanka’s territorial sea but within its designated search and rescue region, triggering obligations under the International Convention on Maritime Search and Rescue (1979). Survivors were transferred to Karapitiya Teaching Hospital in Galle for treatment. (newsfirst.lk)
Hegseth characterised the strike as a “quiet death” for a warship that “thought it was safe in international waters,” and described it as the first time since the Second World War that an American torpedo has sunk an enemy ship. The Pentagon also released monochrome periscope footage showing a torpedo detonation and the vessel breaking apart. (time.com)
Open‑source records indicate that while the United States has not acknowledged a submarine torpedo sinking of an enemy ship since 1945, other navies have. Pakistan’s PNS Hangor torpedoed INS Khukri in 1971 and the UK’s HMS Conqueror sank the ARA General Belgrano in 1982. Media reporting has therefore framed Hegseth’s description as accurate for the US specifically, but not globally. (news.usni.org)
Sri Lankan officials initially avoided attributing the cause, reporting only oil slicks, life rafts and people in the water when rescue units arrived, and at one point dismissing early media claims of a submarine attack. Washington’s on‑record confirmation has since removed that ambiguity about the strike itself, while Colombo’s agencies continue recovery operations. (apnews.com)
IRIS Dena is a Moudge‑class surface combatant that Iran describes domestically as a destroyer but international reporting often terms a frigate. The ship had featured at India’s International Fleet Review in Visakhapatnam in February 2026 and was transiting in deep water on its return leg when it sent the distress call, according to Sri Lankan and Indian reporting. (theguardian.com)
Under the law of armed conflict at sea, enemy warships are military objectives. In an international armed conflict, attacks may be conducted against such objectives in international waters subject to the principles of distinction, proportionality and precautions. The International Committee of the Red Cross and the US Department of Defense’s Law of War Manual set out these rules, which also require due regard for neutral states and nearby maritime traffic. (icrc.org)
Because the position lay in Sri Lanka’s search and rescue region, not its territorial sea, Colombo’s response drew on treaty duties rather than belligerent obligations. The International Maritime Organization explains that parties to the SAR Convention maintain Rescue Coordination Centres and must organise assistance regardless of the flag of the vessel in distress-a point Sri Lanka’s ministers underlined when justifying the rapid deployment. (imo.org)
The strike widened hostilities geographically beyond the Gulf. Turkey said NATO air and missile defences intercepted an Iranian ballistic missile headed toward Turkish airspace on 4 March; US officials indicated this did not trigger Article 5. The same day saw continued Iranian missile and drone activity across the region and further Israeli strikes, underscoring the risk of spillover. (aljazeera.com)
For maritime actors, the policy questions now concentrate on risk to naval units and commercial shipping along Indian Ocean routes. The Guardian reported significant disruption to flows through the Strait of Hormuz amid the wider campaign, and insurers are reassessing premiums on voyages transiting exposed corridors. (theguardian.com)
Sri Lanka has publicly positioned itself as neutral, calling for restraint and immediate de‑escalation while focusing on humanitarian obligations. Following confirmation of the death of Iran’s Supreme Leader Ali Khamenei on Saturday 28 February, senior Sri Lankan figures, including the foreign minister, offered condolences at Iran’s embassy in Colombo-another marker of Colombo’s effort to keep diplomatic channels open while managing a sensitive rescue. (newswire.lk)
As of Thursday 5 March 2026, Sri Lanka reports 87 bodies recovered and 32 survivors from the sinking of IRIS Dena. With search operations continuing and the legal and strategic ramifications still unfolding, officials in Washington, Tehran and regional capitals face decisions that will shape rules‑of‑the‑road at sea for the duration of this crisis. (apnews.com)