US Marines board cargo ship in Arabian Sea to enforce Iran blockade

U.S. Marines on Tuesday boarded and searched a commercial vessel in the Arabian Sea suspected of attempting to reach Iran in violation of the American naval blockade, the military said, before releasing the ship after confirming it was not headed to an Iranian port.

The Boarding

Marines from the 31st Marine Expeditionary Unit conducted a Visit, Board, Search, and Seizure operation on the M/V Blue Star III, a small containership, U.S. Central Command said in a post on X. Video released by the command showed troops fast-roping onto the vessel's deck and entering its bridge.dvidshub+2

The Blue Star III, a 4,259 deadweight-ton vessel with a capacity of 215 containers, departed from Port Qasim, Pakistan on April 16 and was listed as bound for Oman. The ship is not sanctioned but appears to be stateless, having cycled through registrations in Comoros, Tanzania, and the South Pacific island nation of Niue, according to The Maritime Executive. It has been operated by an Oman-based company since 2021.maritime-executive+1

After the search, CENTCOM said forces "released the vessel after conducting a search and confirming the ship's voyage would not include an Iranian port call".moneycontrol+1

Blockade Enforcement Intensifies

The boarding is part of a broader campaign to enforce the U.S. naval blockade of Iranian ports, which began on April 13 under orders from President Donald Trump following the collapse of the Islamabad Talks aimed at ending the 2026 Iran war. CENTCOM said 39 vessels have now been redirected to ensure compliance, up from 34 reported late last week.wikipedia+3

The operation follows more forceful interdictions earlier this month. On April 19, the USS Spruance fired on the engine room of the Iranian-flagged cargo ship Touska in the Gulf of Oman after it ignored warnings for six hours, and Marines took custody of the vessel. Days later, U.S. forces boarded the oil tanker M/T Tifani, previously sanctioned for smuggling Iranian crude.npr+2

Dual Blockade Strains Global Shipping

Pentagon chief Pete Hegseth has said the blockade will last "as long as it takes," while the top U.S. military officer General Dan Caine has stated it "applies to all ships, regardless of nationality, heading into or from Iranian ports". The blockade involves more than 10,000 troops, over a dozen warships, and upward of 100 aircraft.militarytimes+1

The enforcement comes amid a broader crisis in the Strait of Hormuz, where Iran has restricted shipping since late February in retaliation for the U.S.-Israeli air campaign. The resulting dual blockade has left hundreds of vessels waiting at either end of the critical waterway, through which roughly a quarter of the world's seaborne oil trade once flowed.wikipedia+1