Strait of Hormuz reopening likely to be delayed to sweep Iranian mines

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Mines placed in the Strait of Hormuz during the Iran war are putting a damper on plans to quickly return shipping traffic to normal under a memorandum of understanding signed this week.

President Trump on Monday said the U.S. military was already “doing a little hunting for a couple of mines,” — an estimated 5,000 of which Iran possessed and could have placed in the waters in and around the strait after the conflict began in late February.

But such an operation — which would need conventional minesweepers, underwater drones and likely the help of allies — could take months to complete and deter shipping companies from ​passing through until assurances are absolute, experts say.

“They’re an unknown, they’re hard to find, and they create a sense of fear that other weapons don’t,” said Steven Wills, a navalist for the Center for Maritime Strategy. “They can just come out of nowhere if they’ve been laid in the right place at the right time. . .. I think it’ll take some time to figure this out.”

Wills said that there could be anywhere from dozens of mines up to 100 to 200 in the waters in and around the strait. The varieties could range from those that float just beneath the water’s surface to those that sit on the seafloor and are triggered by sensors.

He personally predicted the figure to be on the lower end as mines are placed through small boats controlled by the Iranian Revolutionary Guard Corps and each boat could carry only one or two.

“I don’t think they laid a huge number, but it’s hard to tell until you get people in there and start looking and start generating some reports,” he said.

Bryan Clark, an expert in naval operations with the Hudson Institute, also guessed the Iranians laid “maybe a few dozen mines” in the course of the war, mostly at the start as the U.S. quickly started to attack any boats that looked like they were doing so.

But even a few of the floating bombs would be more than enough to deter vessels from traversing the strait because “you can create the perception of a minefield.”

“It serves its purpose, even at that kind of scale,” Clark told The Hill.

He predicted that it would take one to two weeks just to find where all the mines are placed, followed by a couple of months of concerted effort to dismantle and clear the objects before shipping can be returned to normal.

While it remains unclear how many mines could be around the Strait of Hormuz, U.S. officials have said Iran placed a few dozen in the vital shipping lane in early March at the start of the conflict.

The activity kicked off a U.S. response, with Defense Secretary Pete Hegseth on March 10 declaring that Trump directed American forces to eliminate inactive mine-laying vessels in the waterway, “wiping them out with ruthless precision.”

U.S. Central Command later said that it had attacked 16 Iranian mine-laying boats in the region, but it was unclear whether those strikes disabled Tehran’s capabilities.

Now, with a deal to reopen the Strait of Hormuz, set to be signed by Washington and Tehran on Friday, the Navy may soon be sweeping the waterway to assuage shipping companies of their fears.

Wills said the first step is mine hunting: using a ship or unmanned vehicle to figure out a path that a ship can follow to safely move through the area without hitting a mine. He compared the operation akin to working in your yard.

“If you want to walk across your yard in a path and you don’t want to step on any weeds, you walk along and just pull the weed in front of you and toss it to the side to the point where you have a pathway that you can walk across,” he explained.

“So with that you use a ship, a helicopter towed sled, an unmanned vehicle towing a sled, or an unmanned underwater vehicle to basically map a route,” he said.

Clark also said the easiest way to restore access is to find a lane that’s clear of mines, avoiding the weapon until it can be picked up later.

Mind sweeping, on the other hand, is usually done in the wake of a conflict and more akin to mowing the grass, according to Wills.

In that scenario, an unmanned surface vehicle tows behind it an influence mine sweep “to set off magnetic and acoustic mines by booming electromagnetic energy into the water and causing those things to detonate.”

There’s also the traditional method where forces deploy a physical mine sweeper that throws out two big spreads of cable with various sound effect makers and snags on it to physically catch and force mines to the surface. There they are dealt with by explosive ordinance disposal people, “which is a messy process, and of course highly dangerous,” Wills said.

The entire process could take months before many insurance, shipping or oil companies are convinced it’s safe to sail through the strait, potentially holding up tens of millions ‌of barrels of oil that would usually be passing through the shipping lane in times of peace.

During clearance operations after the 1991 Persian Gulf war, for example, it took the U.S. and various allied contingents nearly seven months to clear the hundreds of mines then-Iraqi President Saddam Hussein had ordered laid in the waters around Kuwait City.

Even with the technological advancements since then, the different kinds of mines the Iranians possess could make it tricky to find them all. Tehran could utilize a kind of floater mine with spikes on it, used since World War I, or more modern weapons that sit on the bottom of the sea and are very difficult to find.

“You drop them on the bottom, they look like a rock or a piece of debris, so you have to hunt carefully for those using a variety of sensors,” Wills said.

There has even been some discussion of mines that can move and reposition themselves, which Wills said “are especially scary.”

In any case, “it’s a slow process,” and firms are likely going to need a report from U.S. Central Command assuring them its forces have fully covered the mine threat, he added.

“I think it’ll take some time to figure this out, because you want to achieve that level of confidence, where you can say, ‘yes, we’ve done our due diligence, we’ve swept all the mines, we’ve destroyed them, we’ve hauled them out, and here’s our report,’” Wills said.

Clark also said the Navy would need to share its results with companies, as well as demonstrate that lanes are clear by driving its own ships through with commercial ships to follow behind.

“That’s pretty much how you have to do it, or else they won’t feel confident that it’s safe enough transit,” he said.

He placed the cost estimate for such an operation at “ten of millions” of dollars just in operational costs, including “gas, paying people extra to go out and do this, repair parts, all the stuff that goes along with doing an extra operation that you have not budgeted for.”

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