US sub sinks Iran’s IRIS Dena off Sri Lanka, 87 dead

Here’s what we know and when we know it. In the early hours of Wednesday 4 March 2026 local time, Sri Lanka answered a distress call from the Iranian warship IRIS Dena about 40 nautical miles south of Galle. By evening, officials said 87 bodies had been recovered and 32 sailors rescued, with ship documents indicating roughly 180 people were aboard. In Washington, US defence secretary Pete Hegseth said a US submarine fired a torpedo that gave the ship a “quiet death.” (indianexpress.com)

Place matters. The site was outside Sri Lanka’s 12‑nautical‑mile territorial sea (so, in international waters) but inside Sri Lanka’s designated search‑and‑rescue region. That difference explains why Sri Lankan crews led the rescue even though the sinking happened beyond its waters; under the International Maritime Organization’s SAR Convention, states coordinate rescues within their assigned regions. A navy spokesman said teams found oil patches and life rafts on arrival. (un.org)

You may have seen conflicting early claims. Sri Lankan officials initially rejected reports of a submarine attack as they focused on rescue, then the Pentagon released footage and Hegseth publicly attributed the strike to a US submarine. In fast‑moving emergencies at sea, first statements are often cautious while evidence is verified. (theweek.in)

Who was IRIS Dena and why was she here? Dena is a Moudge‑class Iranian frigate launched in 2015 and assigned to Iran’s Southern Fleet. She had just taken part in India’s International Fleet Review and Exercise MILAN 2026 in Visakhapatnam and was sailing home when the incident occurred. (indianexpress.com)

Hegseth also called it the first time since World War Two that an American submarine had sunk an enemy ship with a torpedo. Other navies have done so in the modern era: Pakistan’s PNS Hangor sank India’s INS Khukri in 1971, and the UK’s HMS Conqueror sank Argentina’s General Belgrano in 1982. Those examples help you place yesterday’s event in naval history. (time.com)

What we can see. A clip released by the US Department of Defense shows a single strike that lifts the vessel’s stern before the ship breaks and explodes-consistent with a torpedo detonating beneath or near the keel. Visuals can be compelling, but remember they show only one angle and moment in time; investigators will still piece together a full timeline. (apnews.com)

Zooming out helps. The sinking came amid a wider war that escalated after the killing of Iran’s Supreme Leader Ayatollah Ali Khamenei on Saturday 28 February 2026. Since then, the US and Israel have struck targets in Iran and its allies, while Iran has launched missiles and drones across the region. (apnews.com)

Spillover is real. On Wednesday 4 March, Turkey said NATO air and missile defences intercepted an Iranian ballistic missile headed towards Turkish airspace-an incident officials said did not trigger NATO’s collective‑defence clause. These events show how quickly a maritime incident can sit inside a much bigger picture. (news.usni.org)

Where Sri Lanka stands. Colombo says it remains neutral and has urged “utmost restraint and immediate de‑escalation,” even as it coordinated rescue efforts and moved survivors to hospital in Galle. That’s a practical example of how neutrality and humanitarian duty can operate together. (mfa.gov.lk)

Let’s pause for key terms you’ll meet in coverage. International waters means seas beyond a state’s territorial sea, which UNCLOS caps at 12 nautical miles from the coastline. A Search and Rescue Region (SAR) is a mapped zone where a country accepts responsibility to coordinate rescues under the IMO’s SAR Convention. A torpedo is a self‑propelled underwater weapon designed to explode against or beneath a hull. Knowing these helps you read reports with confidence. (un.org)

Reading the timeline well. Times in statements can clash because agencies speak from different time zones: Washington briefings on “Tuesday night” can still be “Wednesday morning” near Sri Lanka. When you compare updates, match them to exact dates-here, 4 March 2026 in Sri Lankan Standard Time-to keep the sequence straight. (time.com)

What this means next. For students of geopolitics and the sea, watch three threads: any formal inquiry into the strike’s legality, regional missile and drone activity around allied states, and how Indian Ocean navies adjust exercises and patrols after an attack so close to a recent fleet review. We’ll keep updating as verified information lands. (lemonde.fr)