Why Iran’s ‘mosquito fleet’ remains a potent threat in the Strait of Hormuz

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Iranian warships sunk by US and Israeli attacks litter naval harbours along the Persian Gulf coast, but what is sometimes called a “mosquito fleet” lurks in the shadows.

It is a flotilla of small, fast, agile boats designed to harass shipping, and it forms the heart of the naval forces deployed by the Revolutionary Guard, a force separate from Iran’s regular navy.

These boats, and especially the missiles and drones that the Guard navy can launch from them, or from camouflaged sites onshore, have been the main threat stymieing shipping through the Strait of Hormuz.

Iran had vowed to keep the strait closed until there was a ceasefire in Lebanon.

On April 17, senior Iranian officials made conflicting statements about whether that truce had prompted Iran to open the strait. On April 18, Iran’s military said the waterway had “returned to its previous state” and was “under strict management and control of the armed forces”.

Welcoming the initial Iranian announcement of the opening, US President Donald Trump pronounced the Hormuz situation “over”, while stressing on social media that the US blockade of Iranian ports would remain in place until a peace deal was reached.

The task of keeping the strait closed would fall to the Guard navy.

“The IRGC navy works more like a guerrilla force at sea,” said Professor Saeid Golkar, an expert on the Guard and a political science professor at the University of Tennessee at Chattanooga.

“It is focused on asymmetrical warfare, especially in the Persian Gulf and the Strait of Hormuz,” he added. “So instead of relying on big warships and classic naval battles, it depends on hit-and-run attacks.”

During the war, at least 20 vessels were attacked, according to the International Maritime Agency, a United Nations agency. The Guard navy rarely claimed the attacks, which analysts said were most likely carried out by drones fired from mobile launchers on land, which generate a faint footprint, difficult to trace.

On April 8, after a two-week ceasefire in the war was announced, General Dan Caine, chair of the Joint Chiefs of Staff, said more than 90 per cent of the regular navy’s fleet, including its main warships, sat at the bottom of the ocean.

An estimated half of the Guard navy’s fast attack boats were also sunk, Gen Caine said, but did not specify how many. Estimates of the overall number range from hundreds to thousands; it is difficult to count them.

The boats are often too small to appear on satellite images, and they are moored along piers within deep caves excavated along the rocky coastline, ready to be deployed in minutes, analysts said. Their arsenal poses a major threat to commercial ships in the Gulf and the strait.

“It remains a disruptive force,” said Admiral Gary Roughead, a retired chief of US Naval Operations. “You never quite knew what they were up to and what their intentions were.”

Stepping in where the regular Navy couldn’t

The Guard land forces were formed soon after the 1979 Islamic Revolution because its leader, Ayatollah Ruhollah Khomeini, did not trust the regular army to protect the new government.

The Guard navy was added around 1986. The regular navy had proved reluctant during the Iran-Iraq war to attack oil tankers from Iraq’s financial backers, Kuwait and Saudi Arabia, said Dr Farzin Nadimi, a specialist on the Guard navy at the Washington Institute, a policy think tank in the US capital.

Eventually those attacks ratcheted up, and the United States then deployed warships to escort tankers. One of them, the USS Samuel B. Roberts, almost sank after hitting an Iranian mine. In a subsequent battle, the US Navy scuppered two Iranian frigates and a number of other naval vessels.

Three years later, the Iranians watched as the US laid waste to the Iraqi military during the first Persian Gulf war.

That combination of events convinced Iran that it could never prevail in a direct confrontation with the US military, so it developed a stealth force to harass ships in the Gulf, Dr Nadimi said.

The Guard navy has an estimated 50,000 men, he said, and divides its forces into five sectors along the Gulf, including some presence on many of the 38 Gulf islands that Iran controls.

Overall, it has constructed at least 10 well-hidden, fortified bases for attack boats. One, Farur, is the center of operations for the naval special forces, whose equipment, even their sunglasses, are modeled on their US counterparts.

“The IRGC navy has always believed that it is at the forefront of the confrontation with the Great Satan, and has been in constant friction with the Americans in the Gulf,” Dr Nadimi said.

An arsenal of small, nimble boats

Iran started by using recreational boats mounted with rocket-propelled grenades or machine guns, naval analysts said. Over the years it built a range of specially designed small boats, as well as miniature submarines and marine drones. Iran claims that some of those boats can reach speeds of more than 100 knots, experts said.

The Guard navy also recently developed larger, more sophisticated warships, many of which were targeted in the war, said Mr Alex Pape, the chief maritime expert at Janes, a defense analysis firm. Those damaged included its largest drone carrier, the Shahid Bagheri, a converted container ship that could also launch anti-ship missiles.

To counter a potential swarm of smaller boats, US warships have high-caliber cannons and other weaponry, experts said. Commercial vessels, though, have no way to fend off such attacks.

But the Iranians have never tested swarm attacks of small boats in combat, said Mr Nicholas Carl, an Iran expert at the American Enterprise Institute, a Washington think tank.

Since Mr Trump on April 13 imposed a naval blockade on ships traveling from Iranian ports, even the most powerful US warships are avoiding spending any time patrolling in the vicinity of the narrow Strait of Hormuz. There is little room to maneuver and almost no warning time to ward off a drone or a missile fired from nearby, experts said.

The US warships enforcing the blockade are likely to remain outside the strait, in the Gulf of Oman or even farther, in the Arabian Sea, where they can monitor shipping traffic but are far more difficult for the Guard to attack, experts said.

On April 15, Iran warned that it could expand operations into the Red Sea, another key shipping route in the region, through its proxy force in Yemen.

A long history of confrontation

The Guard navy has long played games of cat-and-mouse with the US military inside the Persian Gulf. Adm Roughead remembers that in the 1990s and 2000s, the small attack craft would approach American warships at high speeds and then veer off when they were half a mile away.

Drone warfare has amplified the danger level, he said. Drones are cheap and sometimes hard to detect, but they can inflict significant damage on a warship costing billions of dollars.

Occasionally the Guard navy has fought directly with American or other forces. In early 2016, it captured two small US naval boats. The 10 sailors, filmed on their knees, were later released unharmed. The episode caused an uproar in the United States.

Brigadier General Mohammad Nazeri, a founder of the Guard naval special forces, who led that attack, achieved cultlike status in Iran. He inspired a reality show on state television, The Commander, which ran for five seasons.

Each season, about 30 contestants competed for the chance to become a naval commando. They demonstrated their survival skills or feats of daring like jumping off cliffs into the Gulf. After each round, viewers voted for their favorite “hero”. NYTIMES