Closing NATO’s Deterrence Gap

By Agnia Grigas, Project Syndicate | Oct 7, 2026

With Russian provocations against NATO member states growing more frequent, the alliance urgently needs to develop a credible doctrine of punitive deterrence to guide its response to acts of aggression that fall below the threshold of war. Mere territorial defense is not enough.

VILNIUS—On September 23, just a week after NATO aircraft shot down a drone that had entered Lithuanian air space from Belarus, a Russian military helicopter flying out of Kaliningrad briefly breached Polish airspace. Neither intrusion was an isolated episode. A growing catalogue of security incidents shows that the Kremlin’s war of aggression against Ukraine is pressing ever more ominously on NATO’s borders.

As reassuring as it was to see NATO scramble fighters intercept and destroy the drone, the broader pattern of encroachments raises a difficult question: What will Europe and NATO do about these provocations? NATO has become increasingly capable of defending against them, but it has been much less willing to impose costs on Russia for its aggression.

This failure of deterrence goes to the heart of Europe’s security problem. On one hand, NATO’s frontline states, like Estonia, Latvia, Lithuania, Poland, and Romania, are responding to Russian military and hybrid threats, as well as investing heavily in air and missile defense, counter-drone systems, cyber resilience, critical infrastructure, and civil preparedness. NATO has reinforced its eastern flank, and European governments are rebuilding military capabilities after decades of underinvestment. But, as I show in a new Atlantic Council report, there is a persistent gap: NATO members’ response remains overwhelmingly defensive and reactive.

This shortcoming matters because Russia’s pressure on NATO’s eastern flank is no longer confined to conventional military threats. Its aggressive actions increasingly come in the form of hybrid warfare, with drones crossing borders, GPS signals being disrupted, infrastructure being sabotaged, and cyberattacks targeting governments and businesses. Many operations are deliberately ambiguous, intended to allow the Kremlin to probe the alliance without clearly crossing a threshold that would trigger a collective response. And, of course, Russian intelligence services operate across Europe—though, fortunately, the open door that former Hungarian Prime Minister Viktor Orbán had offered them is now closed.

Having learned to live with chronic Russian pressure, NATO’s frontline countries are preparing not only for a possible invasion, but also for a prolonged period in which peace and conflict overlap. Yet NATO itself continues to think in discrete terms: Is this latest provocation serious enough to trigger Article 5? Was that drone incursion deliberate? Can that sabotage be conclusively attributed to Russia? Does this incident warrant escalation?

Such caution is understandable. But caution can itself be risky. As these cases accumulate, they create a dangerous incentive for the Kremlin to keep testing NATO’s tolerance.

Deterrence requires more than the ability to absorb an attack. Your adversary must believe that attacking you will leave it worse off. NATO has invested heavily in what strategists call deterrence by denial: making it harder for Russia to penetrate allied territory or achieve its objectives. What it needs now is deterrence by punishment. The next time multiple drones enter Polish or Baltic airspace, or a Russian-linked operation targets an arms manufacturer, or sabotage damages critical infrastructure, the consequences should not be limited to the usual statement of condemnation.

Punishment need not entail a military escalation. NATO and the European Union can use many tools, including targeted sanctions against individuals and industries, diplomatic expulsions, restrictions on travel and commercial access, tighter controls on Russian and Belarusian transit, coordinated cyber measures (where legally authorized), and strategic communications that expose Russian operations and the networks behind them.

The essential point is predictability. The Kremlin must be made to understand beforehand that certain actions will produce certain costs. That would not eliminate the risk of escalation, but it would be better than the current approach. If Russia repeatedly encounters defensive measures but few meaningful consequences, it may conclude that NATO has many red lines but few penalties for crossing them. That is a dangerous message to send, especially from the perspective of countries on NATO’s eastern flank.

Lithuania, Latvia, Estonia, Poland, and Romania are already carrying a disproportionate share of the burden. They are strengthening their militaries, protecting infrastructure, preparing their populations, and confronting Russian and Belarusian pressure on a daily basis. They cannot also be expected to compensate indefinitely for ambiguity at the NATO level.

Although Europe must assume greater responsibility for its own defense—as most governments already recognize—American engagement remains indispensable. As the United States reassesses its military posture in Europe, uncertainty about its future presence and collective-defense commitments on the continent risks becoming another variable in the Kremlin’s calculations.

Fortunately, NATO does not need a strategy of automatic retaliation, nor does it need to turn every ambiguous incident into a potential military confrontation. What it needs is a credible, coordinated, and predictable response to aggression below the threshold of open war. NATO should develop a clear doctrine for responding to Russian hybrid and kinetic provocations, and establish mechanisms that allow it to act without beginning the debate from scratch after every incident.

Recent events demonstrate that NATO can defend its airspace. That matters enormously to the people who live along its eastern flank. But real deterrence would alleviate the need to shoot down drones in the first place.

Agnia Grigas, a nonresident senior fellow at the Atlantic Council, is the author, most recently, of Beyond Crimea: The New Russian Empire (Yale University Press, 2016) and The New Geopolitics of Natural Gas (Harvard University Press, 2017).