“OUR COMMITMENT to defend…every inch of Allied territory at all times”, declared NATO at its summit last year, “is iron-clad.” That may be true on the ground. But in recent weeks it has seemed shakier in the air. First came a wave of Russian drones, into Poland, on September 9th. Then a trio of Russian MiG-31 fighter jets entered Estonian airspace on September 19th, traversing it for 12 minutes. Days later a wave of mysterious drones shut down Denmark’s main airport and appeared over Oslo. As Donald Trump steps back from Europe and efforts to end the war in Ukraine, Vladimir Putin appears to be turning the screws on the continent.
Since the full-scale invasion of Ukraine in February 2022, Russia’s intelligence services have led a campaign of sabotage and subversion across the continent. Some call this “hybrid warfare”, a reference to its mixture of violent and non-violent means, typically below the threshold of armed conflict. Others talk of the “grey zone” between peace and open war. Military experts sniff at both terms as imprecise or vacuous. But what they represent is very real. A recent study by the International Institute for Strategic Studies, a think-tank, found that incidents of confirmed Russian sabotage against European critical infrastructure rose by 246% between 2023 and 2024, much of it directed at maritime and water-related facilities (see map and chart). On September 17th Lithuania charged 15 people with ties to Russian military intelligence with placing explosive parcels on cargo planes, causing ground fires in Germany, Poland and Britain last year.
That campaign now seems to be migrating into the skies above Europe. For decades Russia has occasionally strayed into the national airspace of NATO allies, which follows national borders and extends 12 nautical miles from a country’s shoreline. But airspace violations have approximately doubled in the past year, according to a Western official. They have also grown more serious. The breach of Estonian airspace was the most egregious such incursion in that country in more than 20 years. The drone barrage into Poland was the largest transgression in the alliance’s 76-year history.
Until this year NATO had invoked Article 4, a clause which triggers consultations among the alliance’s 32 members, only seven times in its history. Now it has been invoked twice in two weeks, first by Poland and then by Estonia. In the incident on September 19th Italy, Finland and Sweden scrambled fighter jets to meet the three Russian planes, which acknowledged the intercept with a wing-wave but did not communicate over radio or change course.
The drone incidents are much murkier. On September 22nd Copenhagen and Oslo airports briefly shut after drones were spotted in and around their airspace. Overnight on September 24th drones once more flew over four Danish airports, including a military air base. Two days later Swedish officials said that drones were observed over the Karlskrona archipelago in the country’s east. Drones were seen over Danish facilities, including an air base, again on September 27th. Not all of this is necessarily hostile action. There were more than 500 illegal drone flights near Norwegian airports last year, though most (and possibly all) were probably operated by hobbyists rather than the Kremlin’s saboteurs.
Nevertheless, Denmark seems convinced that the recent incursions were no accident. “There can be no doubt that everything points to this being the work of a professional actor,” said Troels Lund Poulsen, Denmark’s defence minister. “This is what I would define as a hybrid attack.”
Western officials do not know why Russia has ramped up its poking and prodding. Some allies believe that both the Polish and Estonian incidents were accidental, a function of Russian sloppiness rather than malfeasance, though Poland strongly disagrees. Navigation systems might have gone awry on the MiG-31s that strayed into Estonian airspace, for instance. But even if that is so, Russian sloppiness might itself reflect a deliberate choice by the Kremlin to allow the armed forces to run greater risks. And if the incursions were deliberate probing, then part of the explanation might lie with Mr Trump. In recent days, he has sounded strikingly less friendly towards Mr Putin, suggesting that Russia is a “paper tiger” and that Ukraine could win the war, driving Russia out of its territory altogether. At the same time, however, he has been stepping away from the war in Ukraine, insisting that he will sell—but not donate—weapons for Ukraine.
For much of the war to date, Mr Putin’s campaign of subversion was intended to intimidate Europe into reducing its aid to Ukraine and to deter it from expanding that support with more and new types of weapons, such as tanks, jets and long-range missiles. In that, Mr Putin was unsuccessful. The aid kept flowing. But the recent Russian actions are probably aimed at driving wedges between Europe and America, and among European NATO members themselves. Russian incursions create the impression that Europe is unable to protect its airspace, undermining public confidence in governments. They also expose the fact that Mr Trump has little appetite to back his European partners in a moment of crisis. And they accentuate Europe’s internal splits over how to respond.
Consider the debate unfolding within NATO. Some would like the alliance to punch back hard. “If another missile or aircraft enters our space without permission, deliberately or by mistake, and gets shot down…please don’t come here to whine about it,” warned Radek Sikorski, Poland’s foreign minister, addressing Russia. “You have been warned.” On September 23rd Mr Sikorski’s implied threat was unexpectedly endorsed by Mr Trump himself, though he showed little sign of wanting to get involved directly. Some point to the example of Turkey, which shot down a stray Russian jet in 2015.
In practice, many allies want to tread carefully. Major-General Jonas Wikman, the head of the Swedish air force, whose jets were among those that responded to the Estonian incursion, says that he has the delegated authority to shoot down Russian planes if needed. “But we will always refer to the threat level,” he adds. “When we talk about Swedish territory, we talk about proportionality.” In the Estonian incident, NATO was able to track the Russian incursion throughout and the intruders, though armed with air-to-air missiles, posed no apparent threat to the ground.
On paper, each ally has the right to shoot down whatever it likes; it need not wait for permission from NATO. The Baltic states do not have fighter jets of their own—they rely on a rotating cast of allies to patrol their airspace—but their neighbours do. Poland is free to splat the next stray jet. The problem is a political rather than military one. If Russia chose to escalate in response, one concern is that Mr Trump would stand back and that Europeans would squabble among themselves over how far to back the ally that had blown up a Russian aircraft.
NATO allies all agree that the status quo is becoming untenable. Mike Waltz, America’s ambassador to the United Nations, publicly rebuked Russia at a UN session in New York. Marco Rubio, America’s secretary of state, is thought to have done so in private. In Europe, countries are beefing up their defences. Five days after the Estonian incident, more than 100 Polish paratroopers landed on Gotland, a Swedish island that sits in a commanding position in the Baltic sea, as part of a joint exercise. Sweden has also been moving ground-based air defences to the island and increasing the readiness of its air force. “These are intense days and weeks,” says Major-General Wikman. “We need to be able to stay calm and have the right posture, and we’re quite confident that we are on the right track for that.”
