Russia is testing Europe's borders, and NATO is losing its ability to deter it

In August, drones carrying explosives were discovered on the grounds of Leipzig airport in Germany, reportedly intended to destroy Ukrainian cargo planes. In response, Germany closed Russia's consulate in Bonn and stripped Berlin's "Russian House" cultural centre of its right to operate — while experts warn that Europe no longer has a reliable way to deter the rising tide of Russian sabotage.

Berlin responds, but weakly

For years, propagandists on Russian state television have threatened to bomb European capitals, even as Russian diplomats insisted no one was planning a war. Yet according to European intelligence services, Russia is linked to hundreds of sabotage operations — from cyberattacks in Italy and arson in Britain to damage to undersea cables in the Baltic Sea and severed pigs' heads left outside mosques in France. Add to that a relentless stream of disinformation aimed at splitting European societies.

EU foreign policy chief Kaja Kallas said in early September that Russian President Vladimir Putin's goal is to intimidate the continent and force it to abandon its support for Ukraine, adding that he will not succeed. Experts, however, are far less confident: at a moment when attacks on NATO territory are reaching a new and dangerous level, Europe lacks a strong mechanism of deterrence.

Kallas described the failed attack in Leipzig as an operation that "bears all the hallmarks of state terrorism," while acknowledging that no response to it has yet been found. Berlin's reaction has already been criticised as inadequate: former UK defence secretary Ben Wallace wrote on X that if Germany keeps doing nothing in response to Russian attacks, "the tyrant Putin will keep doing the same."

Why NATO can't simply strike back

The situation is complicated by the fact that European NATO members cannot be certain of unconditional support from US President Donald Trump. Article 5 of the North Atlantic Treaty enshrines the principle that an attack on one member is an attack on all. But if allies fail to respond to a growing number of attacks that fall below that threshold, NATO's deterrent power gradually erodes, experts agree.

Kurt Volker, who negotiated on Ukraine during the first Trump administration and now advises Ukrainian authorities on security matters, believes the alliance must be ready for a far tougher response, and that the Kremlin needs to be told in no uncertain terms that its actions will no longer be tolerated. Even he admits, though, that it is unclear exactly where the line lies beyond which Europe is obliged to respond.

Giving a precise answer is genuinely difficult. International law permits a military response only in self-defence — in the event of an armed attack. Lawyers point to a first problem: it must still be proven that a specific attack was carried out by the Russian state itself. If the drone in Leipzig was operated directly by Russian state agencies, their actions are legally attributable to Russia itself. But if the operation was carried out by private individuals or intermediaries, it must be proven that they acted on the instructions or under the control of the state — a far harder thing to establish, notes international law analyst Edmarverson Santos.

A single incident is not grounds for a forceful response

Suppose Russia's involvement in the explosive-laden drone in Leipzig were proven. That would already be a violation of German territorial sovereignty, regardless of the fact that the apparent target was a Ukrainian aircraft. The next question is whether this counts as a "use of force" within the meaning of the UN Charter. There is no precise numerical threshold for that concept, and lawyers interpret it differently.

The drone was carrying explosives and, by all appearances, was meant to cause physical damage — that looks like a use of force. But that is not enough to trigger the right to self-defence: what is required is an actual armed attack, a far higher threshold. The International Court of Justice drew this distinction back in the 1980s, in the case of the United States against Nicaragua, which concerned US military support for the Nicaraguan Contra rebels against the country's left-wing government, including the mining of harbours and strikes on infrastructure. The Court sided with Nicaragua, ruling that the scale and effects of an operation are the decisive factor.

The Leipzig incident on its own does not cross the threshold of an armed attack. But for Russia, this is not an isolated attack — it is part of a broader picture, so-called hybrid warfare — and, in the view of a number of legal scholars, Europe should not examine each case in isolation but instead add the incidents together. The International Court of Justice has taken such a cumulative approach before — for example, in the case concerning Iranian oil platforms, although even there it ultimately found the threshold had not been crossed. There is still no clear-cut criterion for when separate episodes can be lumped together: it requires that all the actions be linked to a single state, be sufficiently interconnected, and be serious in aggregate — and cyberattacks, sabotage, drones, arson and disinformation differ too greatly from one another in perpetrators, targets and methods.

What Europe can do right now

Legal uncertainty does not mean Europe should sit on its hands until some future Russian operation clearly crosses the line into armed attack. That is precisely the central paradox: Russia does not need to cross one clear red line if it can inflict damage through a series of smaller operations just below it. Each individual case — a single act of sabotage, a drone incident — is too small on its own, but their repetition without a coherent response gradually erodes trust in European deterrence.

Carnegie analyst Maksim Beznosiuk suggests allies agree in advance on a "tiered menu of automatic consequences": not every incident should trigger the same response, but Moscow should know in advance that its attacks will carry predictable costs — from sanctions and the expulsion of diplomats to cyber countermeasures and a strengthened military presence on NATO's eastern flank. The EU is moving in a similar direction: European Commission President Ursula von der Leyen proposed in mid-September creating a joint mechanism that would let EU member states respond in a coordinated way to drone incidents, sabotage and cyberattacks that fall below the threshold of armed aggression.

Security expert Liana Fix names more concrete measures: in her view, a tougher response could include seizing tankers that Russia uses to circumvent energy sanctions — something some countries are already doing — while Germany could act more assertively in the intelligence sphere, for instance by launching offensive cyber operations. The point of all these measures is the same: to strip the Kremlin of its main advantage — strategic ambiguity, which lets Russia escalate in small steps, each time betting that any single incident is too minor to warrant a serious response.

Source: seznamzpravy.cz