Iran’s fast-attack boat fleet has become a central risk for shipping through the Strait of Hormuz, raising the prospect that a relatively low-cost naval force could disrupt one of the world’s most important energy corridors.The threat is not built around large warships. It rests on speedboats, fast inshore attack craft, drones, mines, coastal missiles and command networks operated largely by the Islamic Revolutionary Guard Corps Navy. These assets are designed to exploit geography, congestion and uncertainty in a narrow waterway where commercial tankers, naval vessels and patrol craft often operate within close range.
The Strait of Hormuz links the Gulf with the Gulf of Oman and the Arabian Sea. Roughly a fifth of global oil and a significant share of liquefied natural gas exports normally move through the channel, making even limited disruption capable of influencing energy prices, freight rates and insurance costs across Asia, Europe and the wider global economy. China, Japan, South Korea and India are among the economies with high exposure to Gulf energy flows.
Tehran’s naval doctrine has long relied on asymmetric warfare. Rather than matching the United States and its allies ship for ship, Iran has invested in assets that can be dispersed, concealed and deployed in large numbers. Small craft can harass larger vessels, stage swarming manoeuvres, lay mines, guide drones or force ships to slow, divert or wait for escorts. The operational goal is often less about sinking major vessels than making transit appear too risky or too expensive.
The “mosquito fleet” is especially difficult to counter because it blurs the line between routine patrols, coercive signalling and hostile action. Small boats can approach quickly, change course at short notice and operate from islands, coastal bases and sheltered waters. In a crisis, commanders on commercial ships and naval escorts have seconds to distinguish between intimidation and attack.
Iran has demonstrated this pattern over several years through seizures, close approaches and armed confrontations involving tankers and naval vessels. The Revolutionary Guard’s maritime units have used speedboats to surround ships, board tankers and challenge foreign naval patrols. These actions have shown that Tehran can create pressure without immediately triggering a full-scale naval battle.
The risk has intensified as wider tensions around Iran’s nuclear programme, sanctions enforcement and regional conflicts have converged with maritime security. Any threat to Hormuz carries consequences beyond the Gulf because shipping companies, insurers and energy traders respond quickly to signs of danger. War-risk premiums can rise sharply, vessel owners may pause sailings, and buyers can shift to more expensive alternative supplies.
The geography magnifies the danger. The shipping lanes through Hormuz are narrow, and the surrounding waters include Iranian-held islands, shallow approaches and busy commercial traffic. A mine scare, drone strike or seizure of a single tanker can have an effect out of proportion to the physical damage caused. Markets often react to the possibility of sustained disruption rather than confirmed losses alone.
Iran’s leadership views the Strait as both a defensive buffer and a bargaining instrument. Threats against shipping tend to rise when Tehran faces pressure over sanctions, military strikes or diplomatic isolation. By signalling that Gulf energy exports are vulnerable, Iran seeks to raise costs for its adversaries and remind oil-importing economies that escalation would not remain confined to Iranian territory.
The United States and Gulf partners retain overwhelming conventional naval power, including surveillance aircraft, destroyers, patrol craft, mine-countermeasure units and regional bases. Yet superiority does not eliminate the problem. Protecting every tanker, intercepting every small craft and clearing every mine threat across a crowded maritime corridor is costly, labour-intensive and politically sensitive.
Commercial operators face their own dilemma. Continuing to sail through Hormuz under threat preserves supply chains but exposes crews, cargoes and insurers to danger. Suspending transit protects vessels but tightens energy markets and may deepen economic stress. LNG flows are particularly sensitive because Qatar and the UAE rely heavily on the route for exports.
The threat from Iran’s small-boat fleet also has a psychological dimension. A handful of aggressive manoeuvres can force naval escorts to adopt more defensive postures, compel merchant ships to alter routes and create uncertainty over whether future incidents are localised or part of a broader campaign. That uncertainty is itself a weapon.