Russia walks tightrope below NATO's collective-defense threshold as Europe's hybrid-war deterrence falters

Warnings are growing that Europe's existing deterrence strategy is reaching its limits as Russia steadily escalates its operations just below the threshold that would trigger NATO's collective-defense clause. The concern is that without a firm response to Russia's campaign of disruption — carried out through cyberattacks, sabotage and drone incursions designed to avoid providing a pretext for all-out war — the boundaries of acceptable aggression will keep expanding.

European defense and intelligence officials cited last month's attempted explosive drone incursion at Leipzig-Halle Airport in Germany as a case study in the failure of existing deterrence, according to the Financial Times on Sunday (local time). The drone was intercepted before it could detonate, and Russia has been identified as the likely culprit, but officials said Europe must now act collectively.

The FT described the incident as a "harsh wake-up call" about Russia's intensifying hybrid offensive, saying it exposed NATO's inability to deter attacks that fall just short of triggering Article 5 of the NATO charter, which governs collective defense.

"It has become clear that we are not doing enough to deter sub-Article 5 provocations," a senior Western defense official said. "We have sufficient deterrence against conventional and nuclear threats from Russia, but our approach to hybrid warfare really needs to be reconsidered."

Over the past two years, Russia has been accused of using proxies and intelligence services to conduct a range of operations on European soil, including spreading disinformation, launching cyberattacks, firebombing, targeting politicians' homes and severing undersea cables. Germany's government has pointed to Russia as the party behind the Leipzig-Halle drone attempt, though Russia has denied any involvement.

Hybrid warfare involves using spies or outsourced actors to destabilize an adversary's society while preserving plausible deniability. It is relatively cheap to execute but capable of causing significant social disruption, and it is calibrated to stay below the threshold of conventional armed attack — denying the target a justification for full-scale retaliation.

Keir Giles, a specialist in Russian military doctrine at Chatham House, warned that the ambiguity around what actually triggers Article 5 is itself the problem. "As long as that line is not set, Russia will keep pushing it, and if we don't make them pay a price, they will keep going," he said.

Eastern European countries closer to Russia are pressing NATO to respond more forcefully to hybrid warfare and to revisit the threshold for invoking collective defense, so that Russia cannot attack Europe without fear of punishment.

Donald Trump's Russia policy has also been identified as a factor complicating NATO's response. Unlike the Joe Biden administration, which issued strong warnings against any Russian attack on NATO allies, the Trump administration has been downplaying the Russian threat, the FT noted.

Experts described the Leipzig-Halle drone attempt as a watershed moment in Russia's effort to push the boundaries of aggression, and criticized Germany for taking four weeks to publicly attribute the attack to Russia. Hesitancy to openly call out Russia's reckless behavior, they argued, only creates room for further provocation.

"It is truly astonishing that Germany did not act immediately after the Leipzig-Halle incident," said Charlie Edwards, a senior research fellow at the International Institute for Strategic Studies. "Germany still seems to be calculating how far it can go without provoking further Russian escalation — that is entirely the wrong approach," he said.