Iran ‘likely’ to be laying Hormuz mines despite US scepticism

• Hegseth: ‘No clear evidence’
• Uncertainty alone creating risk
• Two approaches to clearing mines

It is credible to believe Iran has begun laying mines in the Strait of Hormuz, according to a former British Royal Navy commodore, despite the US defence secretary’s claim there is “no clear evidence”.

Steve Prest, an associate fellow at the defence and security think tank Royal United Services Institute (RUSI), said recent reporting strongly suggested “mine-laying has commenced”.

The New York Times and CNN both disclosed this week that Iran has deployed naval mines in the contested waterway, citing senior intelligence sources.

But speaking on March 13 in Washington, US defence secretary Pete Hegseth maintained there was “no clear evidence” that Iran had placed mines in the strait.

When asked if Iran had laid mines since the conflict started, Hegseth said the US military had “heard them talk about it”, but no incontrovertible proof that they had done so.

Iran is understood to hold mine stockpiles “running into the thousands”, Prest asserted, meaning strategic countermeasures depend less on how many are deployed than the “level of risk” they create for commercial shipping.

Even laying relatively small numbers of mines could be enough to halt traffic, because uncertainty alone has forced shipowners and insurers to reassess the risks of transiting the narrow chokepoint.

“You might not need many,” Prest told AGBI ahead of the defence secretary’s comments. “Once you suspect one mine, you have to assume there may be more.”

Iran’s Islamic Revolutionary Guard Corp could deploy the devices using a range of platforms, including small boats, submarines and potentially unmanned systems, Prest said.

Even a handful of vessels dropping several mines each could create a significant hazard across heavily trafficked shipping lanes.

Naval mines are difficult to detect and potentially catastrophic for large commercial vessels. If a single device is discovered or even suspected, shipping companies and insurers must assume others could be nearby.

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Prest, who previously served as a director of navy acquisition in the Royal Navy, said clearing the threat would require a coalition effort potentially involving Britain and France as well as the US military.

Even under relatively favourable conditions – if hostilities stopped and forces could move quickly – surveying and clearing shipping lanes could take “a week or two”.

If fighting continued, however, the task would become far more complicated.

Before mine countermeasure vessels could operate safely, naval forces would first need to establish what Prest described as a “bubble of security” to protect them from Iranian anti-ship missiles, drones and fast attack craft operating from the coastline.

“If you’re going to force the strait against Iranian will, then you’re going to have to deal with that whole threat in totality,” he said.

“I don’t think any of that is quick, cheap or easy. This is weeks, not days.”

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Navies typically use two different approaches to clearing mines.

The first, known as mine hunting, involves searching the seabed and the water column for mine-like objects using ships or autonomous underwater vehicles. Suspected mines are then inspected and neutralised individually.

The second method, mine sweeping, uses acoustic or magnetic systems designed to mimic the signature of a passing vessel, triggering mines to detonate harmlessly before commercial ships enter the area.

New technologies, including robotic surface vessels and submarines equipped with advanced sonar, can survey seabed areas far faster than traditional mine countermeasure ships

Many of these systems are yet to come fully online in naval fleets, meaning large-scale clearance operations would still depend on assembling a coalition of countries capable of securing the waterway.

“Then you’re probably talking about the level of confidence. How certain do you want to be?” Prest said.

“In effect, how many times do you want to mow the lawn before you declare there are no stones left in the grass?”