When the war against Iran began on 28 February 2026, Tehran entered the conflict with what looked like a form of economic insurance. It had a large merchant fleet, a national oil tanker company and an extensive network of foreign tankers with opaque ownership. It had also accumulated years of experience in selling crude outside the Western financial system. Tehran was betting that this machinery would keep exports moving, however intense the pressures of war and sanctions became.
More than six months later, events have not unfolded as Tehran had hoped. Iranian ships have not disappeared, nor has the so-called “shadow fleet” been dismantled. But the war has widened the gap between the number of vessels on the books and the number actually able to enter Iranian ports, load oil or cargo and leave safely.
The crisis entered a more dangerous phase in September, when US Central Command said it had destroyed eight tankers linked to Iran in two rounds of strikes on 5 and 8 September, near Kharg Island and Jask and in the Gulf of Oman. After the second round, the Islamic Revolutionary Guard Corps said it had targeted 10 vessels, including eight tankers and two American ships. The escalation shows that tankers have gone from being instruments for circumventing sanctions to direct targets in the war.
The size of Iran’s merchant fleet cannot be reduced to a single figure. The various estimates measure different categories: vessels registered under the Iranian flag; ships owned or managed by Iranian companies even when they fly other flags; and foreign tankers carrying Iranian oil as part of the “shadow network”.
According to figures announced by the Islamic Republic of Iran Shipping Lines (IRISL) in October 2025, the group’s assets included 144 vessels with a combined capacity of around five million deadweight tonnes, including space for 160,000 20ft equivalent units. The Singapore-based commercial platform MagicPort estimates that the National Iranian Tanker Company (NITC), meanwhile, operates 53 vessels with a combined capacity of almost 13 million deadweight tonnes.
The two companies perform different functions. IRISL carries containers and general cargo, while NITC transports crude oil and petroleum products. Disruption to the fleet therefore does not merely mean lost oil revenue; it also affects imports of food, industrial equipment, electronics and spare parts that the Iranian economy needs every day.
A market, not a fleet
Iran’s “shadow fleet” was born of the sanctions that prevented conventional shipping companies, insurers and banks from serving Tehran’s exports. It does not operate as a single national fleet, but as a market of tankers, intermediaries and front companies willing to accept greater risk in exchange for higher returns.
A tanker is typically registered to a single-purpose company established in Hong Kong, the Marshall Islands or the British Virgin Islands, before flying the flag of another country. Its name, flag and manager may change more than once within a short period. Some vessels switch off their automatic identification systems (AIS), transmit false positions or transfer their cargo to another tanker at sea to conceal the oil’s origin before it reaches the buyer.
The International Maritime Organisation defines the “shadow fleet” as vessels engaged in illegal operations intended to circumvent sanctions or evade safety, environmental and insurance rules. Even so, the term has no single, universally accepted commercial definition, which is why estimates of the network’s size vary according to the organisation producing them and the criteria it uses.
Since the beginning of 2026, the US Treasury has sanctioned more than 100 vessels linked to Iran’s “shadow fleet”. That figure represents the ships Washington identified and decided to sanction during the period, not a complete count of the network. One round of sanctions included tankers flying the flags of Barbados, Mozambique, Vanuatu and the Marshall Islands, while their owners and managers were registered in China, Hong Kong and elsewhere.
This structure is the secret of the network’s resilience. When a tanker or company is sanctioned, the vessel’s name, flag and registered owner can be changed. Yet the same structure is also a source of vulnerability, because tanker operators are not necessarily lasting allies of Tehran. They are investors weighing the profit from each voyage against the risk of having their cargo seized or losing the ship itself.
Before the war, the main challenge facing “shadow tankers” was concealing the origin of their oil and avoiding the banks, insurers and authorities that enforce US sanctions. Today, they must cross an active war zone and contend with a naval blockade, the threat of mines, military interceptions and attacks involving missiles and drones.
According to data from the ship- and energy-tracking companies Windward and Vortexa, Iranian oil exports fell by 43% during the first two months of the war. After the United States imposed its blockade on Iranian ports on 13 April, US forces had redirected 44 Iranian vessels, or ships connected to Iranian trade, by the beginning of May.
Exports did not, however, stop completely at every stage. Following a temporary understanding in June, dozens of tankers resumed sailing through a corridor close to the Iranian coast, allowing large quantities of crude oil and petroleum products to leave the country. The respite was short-lived. The collapse of the understanding and the reimposition of the blockade in mid-July erased most of the improvement.
By early August, activity at Kharg Island had subsided. By 9 September, ship-tracking data had detected no very large crude carrier leaving with Iranian crude since 12 July, although the disabling of AIS transponders makes it impossible to conclude that movements had ceased altogether. On 8 September, only six commodity-carrying vessels passed through the Strait of Hormuz, compared with roughly 125 commercial ships a day before the war.
This is where the distinction between a fleet that exists and one that can operate becomes clear. Iran may own, or charter, dozens of tankers, but their usefulness diminishes if they remain empty outside the Gulf or gather offshore near its ports. A concentration of tankers off the Iranian coast may be evidence of a bottleneck and the accumulation of floating storage, rather than a sign of recovering exports.
Kharg: the critical weak point
Around 90% of Iran’s crude exports pass through Kharg Island. Before the war, Tehran accelerated loadings from the island and shipped out large quantities of oil to reduce stocks exposed to attack. Windward data show that loadings reached around 2.2 million barrels a day in February, before falling to 1.25 million barrels a day in April and approximately 600,000 barrels a day after the blockade was imposed.
In September, the strikes were extended to the tankers themselves. On 5 September, US Central Command said it had disabled the Downy off Kharg and the Stark 1 near Jask, and destroyed the empty Kylo, also known as the Noxen, in the Gulf of Oman. On 8 September, it said it had destroyed another five tankers: the Kaviz, Charminar, Horizon 1 and Riesco in the Gulf of Oman, and the Derya near Kharg Island. According to US Central Command, the crews were instructed to abandon the vessels before they were struck.
The loss of a tanker does not merely mean the loss of its potential cargo. Large vessels are capital assets that take years to build, and Iran cannot readily replace them under restrictions on financing, engines, marine equipment, classification and insurance. Their targeting also deters foreign tanker operators that had been willing to bear the risk of sanctions but did not necessarily enter the trade prepared to face military attack.
