US Marines Board Iranian Ship Blue Star III in Strait of Hormuz Blockade

U.S. Marines from the USS Tripoli fast-roped from MH-60 Seahawk helicopters onto the deck of the suspicious container ship Blue Star III on Tuesday. The vessel was heading for Iran. That brings the total to 39 vessels turned back, boarded or seized since April 13.

"The blockade has been unbelievably effective," President Donald Trump said on Sunday. Economic pressure drives the blockade, but it carries military impact beyond the Strait of Hormuz.

"We seized their sanctioned ships, and we will seize more," U.S. Secretary of War Pete Hegseth said at the Pentagon on Friday, April 24. "Our blockade is growing and going global," Hegseth added.

The global push has China on edge. The country imports at least 70 percent of its oil, with 90 percent moving by sea. Iran supplied 14 percent of China's imports last year, and Russia added 18 percent. Most of that oil travels on shadow fleet tankers.

The action began in the early hours of Sunday, April 19, when the Iranian-flagged Merchant Vessel Touska tried to enter the Strait of Hormuz for the port of Bandar Abbas. Touska moved at 17 knots under darkness. The U.S. Navy guided-missile destroyer USS Spruance waited in position.

Spruance had intercepted another Iranian ship five days earlier. At 9 a.m., after warnings, Spruance fired nine inert 5-inch shells into Touska's engine room, stopping the vessel. At 4 p.m., Marines from USS Tripoli air-assaulted aboard and took the ship and crew into custody.

Admiral Samuel Paparo, commander of U.S. Indo-Pacific Command, directed forces that captured two Iranian oil tankers last week. The Motor Tanker Tifani, a shadow fleet vessel, hauls oil from Iran to waters off Malaysia for transfer to China-bound ships. U.S. forces boarded Tifani, seized the bridge and took custody of 1.9 million barrels of oil worth $171 million at $90 per barrel.

Next, forces boarded and seized the Motor Tanker Majestic X in the Indian Ocean. The stateless vessel was sanctioned in 2024 for carrying Iranian oil. Both Tifani and Majestic X now head west toward the U.S. Military Sealift Command base at Diego Garcia. The Blue Star III crew convinced Marines the ship was not bound for Iran, so they released it.

This year marks the largest haul of captured enemy vessels since President Franklin D. Roosevelt requisitioned 90 foreign merchant ships in U.S. harbors in 1941. U.S. Southern Command seized seven Venezuelan oil tankers in the Caribbean in January.

Russia's shadow fleet also faces risk. President Vladimir Putin built a ghost fleet of more than 770 tankers to dodge sanctions after the 2022 Ukraine invasion. The fleet moves 3.7 million barrels of oil per day, mostly to China.