Can America clear the Strait of Hormuz of Iran’s drones and mines?

The strait of Hormuz is tricky for mariners at the best of times—narrow, congested and often hazy. In times of conflict, it can be a death trap, overlooked by mountains. Tankers carrying oil, refined fuels and liquefied natural gas have all but stopped sailing through the passage since the start of Operation Epic Fury, causing a shuddering energy shock. Can America clear the waterway by military force?

At least 16 vessels have been struck in the Gulf region, including a Thai-flagged bulk carrier in the strait and two fuel tankers in Iraqi waters on March 12th. The Pentagon did not confirm reports that Iran had started to mine the strait. Mr Trump warned that his response to any mine-laying “will be at a level never seen before”. American forces have sunk much of Iran’s navy, including 16 mine-laying vessels, some of them small speedboats.

The president has offered military escorts for tankers if necessary. This is an echo of Operation Earnest Will in the 1980s, at the height of the Iran-Iraq war, when America reflagged Kuwaiti tankers and protected them in transit. European countries and Pakistan are also talking of sending escorts.

More than a quarter of global seaborne oil exports pass through the waterway. Some 46 fuel tankers sailed the passage every day in the weeks before the war, according to data from Vortexa, a market-intelligence firm. Since then only a handful have braved it; they appear to include Iranian tankers. China is reported to be trying to negotiate safe passage for its ships, so far to little avail. Meanwhile, laden tankers are bunching up on the western side of the strait, empty ones on the east.

The threat to shipping comes in many forms. In the air, Iran can make use of ballistic and cruise missiles, as well as drones. On the surface it has fast attack boats armed with missiles or explosives. Beneath the waves it can deploy thousands of sea mines and unmanned vehicles, not to mention divers who can place limpet mines on ships at anchor. How much of this capacity has been destroyed is unclear.

Mr Trump has urged shipowners to “show some guts”. But American warships also seem wary. Shipping sources say the navy has declined repeated requests for protection. Chris Murphy, a Democratic senator, said after a classified briefing that military brass “don’t know how to get it safely back open”. For Mark Montgomery, a retired American rear admiral now at the Foundation for Defence of Democracies, a think-tank in Washington, American forces have not yet reduced Iran’s capabilities to the point at which escorts can deal with remaining threats, he says; in any case American destroyers used for air defence are busy protecting aircraft-carriers in the region. If convoys materialise, he adds, they will require surveillance aircraft, warplanes and helicopters overhead, as well as warships. It will not be easy, or cheap.

During the Gaza war the Houthis, a militia in Yemen allied to Iran, stopped much of the sea traffic in the Red Sea and Suez canal by attacking ships in the Bab al-Mandab Strait with cheap drones and missiles. America struggled to destroy their forces and reopen the strait; one aircraft fell off a carrier as it dodged Houthi attacks. Traffic has yet to return to pre-crisis levels—and the Houthis have vowed to resume attacks in solidarity with Iran.

In the past American commanders have insisted that they could reopen the Strait of Hormuz within days or weeks of Iran attempting to close it. But experts point to the cautionary tale of Britain’s failed campaign against the Ottomans in the first world war to force open the Dardenelles, part of the passage between the Black Sea and the Mediterranean. The allies lost several ships trying to fight their way in from the sea. The Gallipoli landings to seize the passage by land turned out to be an even bloodier debacle.

Iran, too, has layered defences and commanding terrain in the Strait of Hormuz, notes Jonathan Schroden of the Centre for Naval Analyses, another American think-tank. “You have to peel the layers of the onion,” he says. “You would first have to tackle the missiles and the drones and the fast boats before you would go after the mines.” Minesweepers are poorly protected and would struggle to operate under fire. America is replacing wooden-hulled minesweepers with littoral-combat ships carrying mine-warfare “packages”, including unmanned drones, though some worry these are unproven.

In the Dardanelles as in the Strait of Hormuz, notes Caitlin Talmadge, a professor at the Massachusetts Institute of Technology, geography allows the defender to draw enemy vessels close to shore, where they can be more easily attacked. “Some of the weapons have changed—I am more worried about projectiles than mines—but the concept has not changed,” she says.

America’s technological advantages are blunted in confined waters. Drones and missiles reach their targets more quickly, for instance. Moreover, warships are in some ways more vulnerable to damage than larger tankers, which often have double hulls; and their superstructure carries expensive equipment, such as radar. In the 1980s escorts typically sailed behind tankers, not ahead of them, to avoid mines.

A big difference with Operation Earnest Will, Professor Talmadge explains, is that in the 1980s the Iranian regime was seeking to avoid all-out war with America at sea, despite various clashes, as it struggled to hold back Iraqi forces on land. “The idea that Iran will be restrained because of fear of escalation seems fanciful,” she says. “It’s already engaged in an existential war for regime survival.”

Alarmed about the economic impact of the oil crisis, Mr Trump has suggested that the conflict will end “very soon”. Yet if the strait remains blocked, he may find it hard to declare victory quickly. ■