A force of three aircraft carrier battle groups, 10 guided-missile destroyers and two US Marine amphibious assault ships will be used to enforce America's blockade of Iranian shipping.
An immense range of intelligence and surveillance assets – from space to submarines – will also be needed to catch any “blockade runners”, naval experts have told The National.
US President Donald Trump hopes that, where his air strikes have failed, his economic throttling of the Strait of Hormuz will force Iran to reopen it. However, to do so he will need the full might of the US Fifth Fleet.
The task will also possibly require American warships to approach Iran’s coastline, making them vulnerable to Chinese-made shore-based anti-ship missile attacks, if they want to intercept ships in the Gulf of Oman.
Navy officers who have conducted boardings have outlined challenges, including the possibility that IRGC troops might be aboard ships.
Carrier command
The commander of the Fifth Fleet, who will oversee the blockade, is probably aboard the USS Abraham Lincoln. The aircraft carrier will form the operations base alongside fellow carriers the George HW Bush and Gerald R Ford, which is returning from repairs in the Eastern Mediterranean.
The carriers’ E-2D Hawkeye surveillance planes will be operating around the clock to search beyond the horizon for rogue ships.
Its F-35 or FA-18 Super Hornet fighters can also be used for rapid “show of force” flyovers of shipping to ensure they comply with orders to return to port.
On each of the two amphibious assault ships are a force of 2,200 US marines. Among them will be teams available to go ashore from helicopters for boarding operations, along with Viper attack helicopters for extra support.
It is a potent force backed up by the well-armed Arleigh Burke destroyers and their host of Harpoon anti-ship missiles, air defence systems and the ability to power ahead at 30 knots.
Ship spotters
American satellites, maritime surveillance aircraft and drones will play a significant role in providing shipping information, including E-3 Sentry AWACS and P8 Poseidons flying from bases in the Gulf.
“They need the intelligence picture to know what is coming from or going to Iranian ports to identify correctly what is and what isn't a potential blockade runner,” said Prof Kevin Rowland, a naval expert at the Rusi think tank.
Every ship in the Gulf of Oman will have to be “marked” by the watchers, understanding which ships have come from which ports.
“The maritime picture is going to have to be very good, and that responsibility will be with the US Fifth Fleet,” said former Royal Navy commander Tom Sharpe.
He also highlighted the “conundrum” US forces will face over whether to come in close to the strait's opening to keep a tight cordon but face the threat of anti-ship missiles, or to keep their distance but risk losing track of the vessels.
“If you back away from the land threat then ships become dispersed and suddenly you've got a massive area to cover,” said Mr Sharpe, who commanded warships in the Arabian Gulf.
Boarding parties
America appears so far to have been able to force ships trying to exit the strait to turn around, but its sailors and marines will be preparing to board ships if they are “non-compliant”, and that comes with its own dangers.
Boarding can be done with fast boats but will more likely be with marines or navy Seals fast-roping from helicopters.
The danger here, said former US marine Jonathan Hackett, is that there might be “IRGC Navy folks on the vessel shooting back at us” as well as merchant sailors coerced into defending the vessel or sabotaging it so that it cannot be moved.
The Iranians could also threaten helicopters by using hand-held surface-to-air missiles.
“If I was one of these vessels, I would have someone standing on the bridge wing with something that looked like a shoulder-launched weapon,” said Mr Sharpe. “That means it has become an opposed boarding and that requires special forces so suddenly you've got a resource problem.”
If a ship refuses to divert or the Americans decide not to board then the destroyers can use their 127mm main gun to fire the classic “shot across the bows”, said Prof Rowland, who spent 30 years in the Royal Navy.
“As a captain I will fire across the bows to make the point. But if the ship does not comply then the next stage is a shot that damages it, not necessarily sinking it, but there are techniques, like a shot flying into the funnel, with no human casualties, that would show intent.”
Another significant issue is what to do with a ship once it has been seized. There are few ports where they can be detained and a security force will be needed to guard multimillion-dollar cargo.
Missiles, mines and subs
Just before the war started, Iran signed a contract with China’s Norinco defence company to provide it with the C-series of anti-ship missiles that could prove deadly to warships coming close to Iranian shores.
This might include the CM-302 supersonic cruise missile, which has a 290km range and a high-hit probability with its 250kg warhead, leading to it being called the “carrier killer”. In addition, there is the threat of mines and mini-submarines.
Mr Hackett also questioned whether having at most 10 Arleigh Burke destroyers to patrol the blockade was adequate.
“There's going to be giant gaps in this even if the US lined all their vessels up along the straits,” said Mr Hackett. “It's realistically nearly impossible to effectively blockade the straits unless there are more assets deployed.”
Another issue in retaining the cordon is that Iran has several ports along the Gulf of Oman coastline, including the harbour at Jask, which could all be used to break the blockade, he added.
