Iran’s ‘mosquito fleet’ brings guerrilla warfare to the Strait of Hormuz

“The Iranian Navy lies at the bottom of the sea, completely destroyed: 158 ships,” the President of the United States boasted on his social network, Truth, on the 13th. In the same message, Donald Trump continued: “What we have not attacked is the small number of what they call fast attack boats.” These small boats of the naval force of the powerful Iranian parallel army, the Revolutionary Guard, which Trump said posed “no great threat,” attacked three large container ships this Wednesday. Two of them were forced to head to Iranian ports for allegedly trying to cross the Strait of Hormuz without the Islamic Republic’s green light.

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As the capture of those two merchant ships reminds us, these boats, capable of launching missiles and drones, are actually considered a crucial weapon in Iran’s hands for controlling that strait, the maritime artery through which, in normal times, 20% of the world’s oil circulates, in addition to other vital raw materials.

Trump’s claim is probably true regarding large ships. It is estimated that the conventional Iranian Navy has been 90% destroyed. However, the Asian country does not need those sunken vessels the Republican alluded to to control Hormuz, Iranian political scientist Vali Nasr assured in a recent interview with this newspaper. The fear of tanker owners — and, above all, insurers — is enough to make many vessels refrain from trying to cross that strait. Tehran also does not need frigates to stop those who venture into those waters. It is enough to use “drones, mines, and cheap weaponry,” Nasr, a former advisor on Iran to the Barack Obama Administration, specified. Or fast boats.

Iran not only has two armies; the regular army and the Revolutionary Guard; it also has two navies. One is the traditional fleet, with frigates and submarines. The other is the naval force of the powerful Iranian parallel army, which has about 20,000 personnel, according to an analysis by the International Gulf Forum, and which has prioritized small, fast vessels.

“The Islamic Revolutionary Guard Corps (IRGC) uses a mosquito fleet” instead of “large warships,” confirms Saeid Golkar, a professor of Political Science at the University of Tennessee at Chattanooga, via text messages from the United States. This expert on the Revolutionary Guard describes how these vessels act “in swarms, approaching at high speed from different directions. In a narrow area like the Strait of Hormuz, this exerts significant pressure on U.S. naval forces.”

The Revolutionary Guard’s fast boats thus constitute the spearhead at sea of a specialty that the country has been cultivating for decades precisely in anticipation of an attack by the United States and/or Israel: asymmetric warfare, designed to counter a conventionally superior enemy. In their case, they execute, explains the specialist, “a form of maritime guerrilla warfare focused on harassment, disorganization, and increasing the cost of U.S. operations, rather than trying to win a traditional battle.”

It is difficult to know how many of these vessels Iran possesses. It is believed to be between several hundred and 1,500, although, in contradiction to what Trump stated days later, the Chairman of the Joint Chiefs of Staff of the United States, General Dan Caine, had assured on April 8 that “half” of the total number — which he did not specify — had been destroyed.

These are boats between 14 and 17 meters long that move at high speed and are, therefore, difficult targets for radars and satellites to detect, and even harder to hit, especially if they attack in large numbers (in a swarm) to saturate the defenses of enemy ships, making them unable to intercept all of them or the projectiles they launch.

In this war, now paused by the fragile ceasefire that Trump extended on Tuesday, the Revolutionary Guard is also combining its maritime strategy with an aerial one, designing attacks with fast boats accompanied by assaults from Shahed series drones. Reuters agency described it with a simile to another insect: “If a bee stings you, it’s a nuisance; if an entire swarm stings you, it can be deadly.”

Shallow waters

The Strait of Hormuz is a 33-kilometer-long stretch of sea at its narrowest point, with shallow waters that the Iranians know like the back of their hand. It is relatively easy to block, especially because oil tankers and container ships must pass through the few channels where the sea is deeper.

The boats of the mosquito fleet easily hide along Iran’s more than 1,700 kilometers of coastline in the Persian Gulf and the Sea of Oman. Not only because of their size, but also because the Revolutionary Guard has built fortified and/or underground bases for them. On March 11, a video aired in January 2025 by Iranian state television, supposedly showing a secret underwater military base, was circulated on X. It alludes — emulating the “missile cities” — to an underground “city of ships” on Iran’s southern coast.

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These boats reach a speed in some cases superior to that of a torpedo: between 40 and 70 knots (75 and 130 kilometers per hour) or even 110 knots (more than 200 kilometers per hour) for the Heydar 100 model, presented in January 2025, equipped with two anti-ship cruise missiles, probably derived from the Chinese technology Nasr 1 model, and with a range of up to 50 kilometers, according to the Defence Security Asia portal. The Heydar 100 weighs, without its armament, only nine tons. It is designed for hit and run operations.

U.S. ships lack their speed and agility and also cannot enter the shallow waters through which these boats can pass.

The U.S. military giant, of course, has fast and agile weaponry. For example, Apache attack helicopters, which are being used against these Iranian vessels, as General Caine confirmed. However, when confronting the Revolutionary Guard’s boats, the United States faces the problem of what military experts call “cost asymmetry.”

Iranian boats are armed with heavy machine guns and, in some cases, anti-ship missiles, according to U.S. Congressional reports. “Although they cannot destroy a major warship, they can damage it, slow down operations, and continuously threaten escalation,” Golkar points out.

They can also, theoretically, shoot down an Apache. An Arleigh Burke-class destroyer — like those in the combat group of the aircraft carrier USS Abraham Lincoln, stationed at the gates of the Strait of Hormuz — costs about 2.7 billion dollars (2.3 billion euros); a latest-generation Apache can exceed 100 million, while Iranian boats are barely worth tens of thousands of dollars.

The design of these vessels, as well as the “swarm saturation” strategy, align with the military doctrine of the Revolutionary Guard, developed since the war with Iraq (between 1980 and 1988) and boosted since the U.S. invasion of that Arab country in 2003. A crucial part of this doctrine involves attacks with cheap weapons that, when combined, generate high defensive costs for the enemy, such as those represented by risking helicopters costing hundreds of millions of dollars, or spending the also very expensive interceptor projectiles to stop Iranian missiles and drones.

Overall, this “asymmetric strategy” allows the Revolutionary Guard to “seriously challenge a much more powerful navy,” says Golkar, who points out that some of these boats are also “prepared for kamikaze-type attacks.” The professor emphasizes how “the concept of martyrdom plays a crucial role” in this matter, as it “reduces deterrence” and makes Iranian tactics “more unpredictable.”

Even with the greater military force of the United States trying to open the Strait of Hormuz, that and other strategies deployed by Iran have led to a situation where “it will take weeks to reach a level that allows safe operation in the strait, and even then, a significant portion of Iran’s [military] assets will remain intact,” highlights Parzin Namidi, an Iranian defense expert at the Washington Institute for Near East Policy, quoted by The New York Times.

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