In the Strait of Hormuz, Iran has developed an asymmetrical naval strategy that is crippling the passage of container ships. This “hemostat” uses guerrilla tactics, after Iran’s “traditional” fleet was almost entirely destroyed by US and Israeli attacks. No longer able to rely on specialized military ships, Tehran is using an unconventional force made up of dozens of small military vessels armed with missiles, machine guns, and drones. Quick and nimble, this “mosquito fleet” is capable of assaulting ships carrying tons of cargo.
In mid-April, US president Donald Trump had reassured the public in a post on Truth Social that Iran’s hemostat fleet did not pose a major problem for the US and Israel. “The Iranian Navy lies at the bottom of the sea, completely annihilated: 158 ships,” Trump wrote. “What we didn’t hit are their small numbers of what they call ‘fast attack boats’ because we didn’t consider them a big threat.” Less than 10 days later, on April 22, an Iranian attack conducted with the small vessels led to the seizure of two large container ships leaving the Strait of Hormuz, changing the course of the war.
Enter the Hemostat Fleet
“Iranian fleets of small boats were created during the Iran-Iraq war, with the purpose of disrupting oil tankers in the Persian Gulf that supported the Iraqi war effort,” says Michael Eisenstadt, an analyst at the Washington Institute for Near East Policy where he is director of the Military and Security Studies Program, who compares them to the “US torpedo squadrons that disrupted enemy naval traffic in the Pacific Ocean and Mediterranean Sea during World War II.”
“The effectiveness of Iran’s fleet of small boats comes from their numbers and their use in swarms, which makes them difficult to counter,” Eisenstadt adds. “Iran has over a thousand of these small boats armed with rockets, machine guns, anti-ship missiles, and mines.” In this way, Tehran can pose a serious naval threat even though much of its military fleet has been destroyed.
“As Iran showed in March, it can close the straits by launching only a few dozen drones against oil tankers and cargo ships in the Persian Gulf,” says Eisenstadt, who has also worked as an analyst for the US military in addition to a 26-year career in the US Army as a reserve officer, with missions in Iraq and Israel.
Between the number of vessels at its disposal and the thousands of support drones for air operation, Iran possesses “much more than it needs to effectively force the closure of the strait,” Eisenstadt says. Then there is its proximity to the Strait of Hormuz, which allows Iran to systematize its deterrence against the passage of container ships and oil tankers. “It is therefore important to see the Iranian threat as multidimensional, involving a diverse range of capabilities to exploit its favorable geographic location,” he adds.
A Tactic in the Hands of the Pasdaran
Iran’s “conventional” navy is separate from the navy of the Islamic Revolutionary Guards Corps, also known as the IRGC or the Pasdaran. But a parallel chain of command has allowed Tehran to develop a diverse guerrilla doctrine, even in their respective operational areas of responsibility.
The hemostat fleet is used by the Pasdaran. As the Hudson Institute, a conservative think tank, explains in a report authored by analyst Can Kasapoglu, “most of the Iranian conventional platforms sunk or put out of commission by allied attacks belonged to … Iran’s regular armed forces,” Kasapoglu adds: “In contrast, the Islamic Republic’s Revolutionary Guardians maintain their own asymmetrical naval component, designed specifically for combat operations in the Strait of Hormuz, much of which has remained intact.”
