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US submarine sinks Iranian frigate Iris Dena in Indian Ocean — 80+ killed

·Indian Ocean, south of Sri Lanka

Defense Secretary Hegseth confirms a US submarine sank the Iranian frigate Iris Dena in the Indian Ocean, ~400nm south of Sri Lanka. 80+ crew killed; 32 of 180 survivors rescued. First US attack on an enemy warship since WWII, and the first action outside the Gulf theatre.

CENTCOM released a brief statement at 21:30 local time confirming that the USS Houston (SSN-713, Los Angeles-class) engaged and sank an Iranian Fateh-class submarine (estimated 600-ton displacement) in the Gulf of Oman. According to CENTCOM, the Iranian submarine was attempting to conduct a covert mine-laying operation in international shipping lanes 80 nautical miles east of Muscat. The submarine was detected by US P-8 Poseidon maritime patrol aircraft, tracked by surface sonobuoys, and subsequently engaged by Houston with Mk-48 ADCAP torpedoes. No survivors have been reported. This is the first submarine-on-submarine combat kill in open ocean operations since WWII. It confirms that the IRGC Navy, despite CENTCOM's claim of 'total Iranian naval destruction,' retained submarine capability through the conflict's opening phase. The mine-laying attempt in major shipping lanes would have been catastrophic — the Gulf of Oman carries ~20% of global LNG traffic. Oman's foreign ministry has been briefed. The kill sets a new escalatory precedent in underwater warfare.
us-navyiranian-navyiris-denawarshipindian-oceannaval-warfarehegseth

Actor responses

United StatesSUPPORTINGmilitary_action

CENTCOM: 'USS Houston engaged and sank an Iranian submarine attempting covert mine-laying in international waters. We will protect freedom of navigation at all costs.'

IRGCOPPOSINGmilitary_action

IRGC Navy: 'We confirm the loss of a submarine in the Gulf of Oman. The crew died as martyrs. Every loss strengthens our resolve. We have more.'

Sources

T1CENTCOM88% reliability
T1Reuters95% reliability
T2Breaking Defense85% reliability
T1AP News95% reliability
T1The Guardian95% reliability
T1Hegseth press briefing90% reliability

Related signals (2)

Pentagon Press Secretary@@PentagonPressSecBREAKING

SecDef Hegseth confirms: A US submarine has sunk the Iranian frigate Iris Dena in the Indian Ocean. 80+ Iranian sailors killed. 32 survivors rescued. The Iris Dena was conducting operations threatening international shipping and US interests. First US warship kill in combat since World War II.

2026-03-04 21:00 UTC
89.0K likes58.0K RT14.2M views
PHAROS NOTEHegseth confirming by name 'Iris Dena' is unusual precision — signals deliberate message to Iran about tracking their major surface combatants globally. 'First warship kill since WWII' framing is being used for deterrence signalling.
U.S. Central Command@@CENTCOMBREAKING

CENTCOM: USS Houston (SSN-713) engaged and sank an Iranian Fateh-class submarine that was conducting a covert mine-laying operation in international shipping lanes in the Gulf of Oman. No US casualties. The submarine posed a direct threat to international commerce and freedom of navigation.

2026-03-04 20:05 UTC
67.0K likes44.0K RT10.2M views
PHAROS NOTEFirst submarine-on-submarine combat kill since WWII is a major naval precedent. Iran's continued ability to deploy submarines despite 5 days of strikes shows the resilience of dispersed naval assets.