Europe, Proportionality, And The Forgotten Language Of Deterrence

In Europe’s strategic discourse, proportionality has become the default reference point whenever the issue of responses to threats and aggressions is raised. Whether the subject is terrorism, cyberattacks, or hostile actions by rival powers, the formula is almost ritual: a proportionate response, calibrated, commensurate to the damage suffered. This approach, seemingly balanced and consistent with international law, hides a structural weakness: Europe has lost the ability to speak the true language of deterrence. Deterrence is not, and has never been, a mechanism of symmetry.

It is built on disproportion, on a psychological construct in the adversary’s mind that works only if he is convinced that any aggression will provoke a devastating, immediate, and unavoidable reaction. By definition, deterrence rests on the principle that the threatened response must be disproportionate—capable of imposing costs vastly higher than the benefits sought. The aggressor must face an unsustainable calculation: modest or temporary gains set against catastrophic losses. This is how deterrence prevents hostile action before it even begins.

The idea of responding in equivalent or proportionate measure, by contrast, sends a very different signal: it communicates that the system is punishable, that aggression has a calculable and possibly bearable price. This is where the fragility of Europe’s current posture lies. Speaking of proportionality does not deter; it invites testing, encouraging adversaries to probe how much pain the system is willing to accept in exchange for limited gains. The Cold War experience demonstrated that deterrence only worked when automaticity and disproportionality were clearly perceived.

A Soviet attack on NATO troops in Germany would not have triggered a proportional reaction on the battlefield, but the very real risk of nuclear escalation. The numbers of conventional forces mattered less than the certainty that any strike would automatically involve the United States, up to the nuclear level. This credibility, rooted in the principle of automaticity, made it highly improbable that Moscow would attempt to test the system.