A drone soars toward a French nuclear-powered aircraft carrier. Twenty drones maneuver over the Danish port of Koege, used for military deployments. The Dutch military tries to bring down drones over Volkel air base in the Netherlands.

Far from the battlefields of Ukraine, drones are forcing European countries to change their thinking about national defense. Despite repeated provocations, NATO members appear ill-prepared for the new drone era, as Russia probes their defenses, seemingly at will.

From August 2024 to February 2026, there were 144 incidents of suspicious drones over a dozen European countries, according to a new report released Thursday by the London-based International Institute for Strategic Studies.

They included the sighting off the coast of Sweden, where a drone near the French carrier was jammed by Swedish forces in February, as well as the ones over Denmark and the Netherlands last year. These did not involve store-bought quadcopters operated by hobbyists or malfunctioning Ukrainian drones straying into NATO airspace, but often complex reconnaissance aircraft flying over military bases and critical infrastructure.

The report’s authors wrote that they “assess it is highly likely” that Moscow carried out a drone campaign in the European skies employing “Russian-linked vessels” in the North Sea and Baltic Sea to launch the aerial drones.

“We see it as a coordinated approach,” Charlie Edwards, one of the report’s lead authors, told reporters at a briefing this week. “We believe the campaign operated with substantial impunity and represents kind of a series of tactical successes for the Kremlin, but a strategic failure of allied defense.”

Individual European countries have named the threat. “We suspect that Russia is behind most of these drone flights,” German Chancellor Friedrich Merz said in October, after a significant increase in drone sightings.

Part of the reason that the response in Europe has been muted, the report found, was because each country “focused on the national response rather than connecting the dots across Europe.” But the full picture comes into focus by looking at it continentwide.

Challenges are many. Militaries often lack the legal authority to act in peacetime by shooting drones down. Even if they have the authority, the risk of civilian injuries, or even fatalities, from falling debris might not be acceptable for a country at peace like Germany or France, the way it is in Ukraine.

Without downed drones and components to study, proving a connection to Russia has been difficult. Some skeptics in Western Europe still say that the overflights are little more than out-of-control quadcopters piloted by amateurs.

“It does not make any sense to believe that these are hobbyist systems,” said Ulrike Franke, senior policy fellow at the European Council on Foreign Relations. She added that sophisticated drones are capable of far more than visual surveillance. Hovering over a base where Ukrainian soldiers are training, for instance, the drones could try to pull cellular numbers that could be used for targeting when the troops return to the front.

An episode at Barksdale Air Force Base in Louisiana this past March demonstrated the vulnerability in the United States as well. According to a statement by Air Force Global Strike Command, the air base “experienced several unauthorized drone incursions that varied in duration and number of drones.” The statement added, “The incident remains under an active federal investigation.”

Ukraine’s audacious sneak attack last summer deep in Russian territory, known as Operation Spider’s Web, demonstrated the risks that drones can pose far behind enemy lines. A similar attack on NATO territory “could totally happen and we aren’t prepared,” Ms. Franke said.

The drone flights in Western Europe are a separate problem from the dangerous, possibly accidental incursions by Russian and Ukrainian attack drones, leading to an apartment building being hit in Romania.

The European Union has been working on a plan for a “drone wall” that would shore up its eastern flank, protecting against Russian drones in the Baltic States, Poland, Romania and elsewhere. It would include radar, acoustic sensors and electronic jamming systems. But so far, the idea has gained limited traction.