In the final days of May, a long-range aerial drone hit a tanker in a port in the Rostov region of Southern Russia. Two days later, three vessels were badly damaged by drones off Turkey’s Black Sea coast.
Similar incidents have occurred regularly since the start of 2026. In January, a drone hit an oil tanker traveling at high-speed off the Turkish coast. In March, an LNG tanker was badly damaged by a drone near Malta in the Mediterranean.
The above attacks – which most assume are a spillover from the Russia-Ukraine war – provide another reminder of the rise of drones as the weapon of choice in contemporary warfare.
But they also illuminate the rising importance in recent years of a non-military weapon – the use of energy sanctions as a tool of coercion. Since the invasion of Ukraine in 2022, Russia has faced the most comprehensive sanctions regime ever imposed on a major energy exporter. In response, Moscow has built-up the largest sanctions evasion program in modern history to redirect energy exports to customers around the world.
Shadow fleets, also known as “ghost” or “dark” fleets, are central to these efforts to deliver sanctioned oil and gas. For example, after Russia’s Arctic 2 LNG plant closed in October 2024 due to sanctions pressure, LNG carriers modified to evade detection were redirected to supply alternative markets. Russia has by far the biggest shadow fleet – estimated at more than 600 vessels. But in recent years, other sanctioned energy producers – from Venezuala to Iran – have also embraced this strategy.
After decades of US sanctions, Tehran has developed one of the most sophisticated evasion capabilities in the world. Since the US blockade of its ports began in mid-April, dozens of shadow vessels linked to Iran have been intercepted by the US navy in Gulf waters.
In all cases, these fleets play an important role in generating the vital income needed to finance domestic economies and, in some cases, military campaigns. It is estimated that Russian revenues from its shadow fleet could be as high as $100bn a year.
Apart from their financial value, these fleets also help energy producers to consolidate existing diplomatic and strategic partnerships and build new ones. This enables them to overcome one of the main objectives of sanctions: to isolate and de-legitimize the targeted state.
Shadow fleets need to adopt a variety of techniques to evade detection.
These include the falsification of vessel registration numbers and the fabrication of manifests and journey routes to disguise cargoes and intended destinations.
It is also increasingly common for ships to turn off their Automatic Identification System (AIS) transponders to prevent tracking and monitoring. GPS spoofing technology that communicates false locations is also regularly deployed.
Stealth or mid-sea transfers are also used to hide the point of origin of cargoes. This is a form of resource laundering whereby oil is moved from one sanctioned tanker to another in international waters, sometimes on multiple occasions during a single voyage.
Another way to disguise the origin of cargoes is to lease vessels registered in non-sanctioned states. One of the ships attacked off the Turkish coast in late May was registered in the Western Pacific island of Palau, the other two in Sierra Leone in West Africa.
Beyond using these “flags of convenience”, shadow fleets also rely on the support of non-sanctioned states or commercial actors within those states to succeed.
It is estimated, for example, that more than 15 ports and terminals across the globe accept sanctioned deliveries and provide shadow fleets with trans-shipment facilities. In recent years, the eastern Malaysian peninsula has become one of the preferred hubs for this activity.
It is also common – using loopholes in anti-money laundering mechanisms – for complex financial transactions to be routed through front or shell companies in non-sanctioned jurisdictions. An increasingly important aspect of this is alternative payment options in crypto and non-dollar currencies.
An ecosystem of maritime insurance and certification vendors is also developing in third-party states. This allows for shadow fleets to gain coverage that would be denied by major western insurance and classification providers. This elaborate shadow fleet network raises an important issue beyond geopolitics.
These fleets – often operating without internationally recognised insurance or seaworthiness certification– can pose serious maritime safety and environmental risks. Many of these vessels, including an estimated 70% of Russian shadow tankers, are operating beyond their recommended retirement age. Aging vessels are more likely to be involved in navigation accidents and oil spills in busy shipping lanes.
These risks increase with shadow fleets because of the deliberate avoidance of port inspections, poor ship maintenance, inadequate crew training, and substandard equipment. The sheer size of the oceans and the high number of ships moving sanctioned cargoes every day complicates detection.
So does the complexity of maritime law. Shadow fleets benefit from contested jurisdiction in disputed waterways. They also take advantage of the lack of coast guard authority in the world’s Exclusive Economic Zones.
Moreover, imposing sanctions is not the same as enforcing them. Enforcement requires a level of multilateral cooperation and coordination that is hard to achieve due to different national priorities.
For example, during recent G7 discussions the US vetoed a Canadian proposal backed by other members to set up a dedicated task force to monitor and crack-down on shadow fleets. The very fact that state actors are resorting to drone attacks on the high seas to stop shadow fleets highlights the limited effectiveness of existing, non-military, enforcement methods.
But these attacks also highlight the centrality of these fleets to a sophisticated alternative maritime infrastructure that exists solely to circumvent energy sanctions. As long there are customers willing to buy sanctioned oil and gas, shadow fleets will continue to adapt and innovate to undermine energy sanctions. And as long as energy-based coercive diplomacy lacks legitimacy across much of the international community, sanctioned energy actors will always find willing partners to support vital shadow networks.
The writer is professor of International Politics and director of the Small States and Energy Studies Programs at Georgetown University in Qatar @RoryDavidMiller