European borders and conflict

Sunday 4 January 2026

Europe’s political geography has never been static. Over the past millennium the continent has been a palimpsest of shifting frontiers, dissolving polities and reconstituted states. Kingdoms have risen and fallen; empires have expanded and collapsed; borders have been drawn, erased and redrawn with striking regularity. This long historical experience does not weaken the modern principle that borders should not be changed by force. On the contrary, it explains why that principle is now indispensable to European order, and why, in the present strategic climate, Europe must be prepared to defend it by military means if necessary.

For much of European history borders were the contingent outcome of dynastic inheritance, conquest or diplomatic convenience. The medieval map of Europe was characterised by overlapping sovereignties, feudal allegiances and ill-defined frontiers. The early modern period brought larger territorial states, yet war remained a routine instrument of territorial adjustment. The partitions of Poland in the eighteenth century, the Napoleonic remapping of the continent, and the nationalist upheavals of the nineteenth century all reaffirmed a brutal continuity: power determined borders.

The catastrophes of the twentieth century were the culmination of this logic. Two world wars, driven in significant part by territorial revisionism, demonstrated the human cost of treating borders as negotiable by force. In response European states attempted something historically novel: the freezing of borders as a foundation of peace. This idea was embedded in the post-1945 international legal order, reinforced in Europe by the Helsinki Final Act of 1975 and later by the broader norms of the post-Cold War settlement. Borders were no longer to be prizes of war but legal facts, alterable only by consent.

This norm was never merely abstract or idealistic. It was a practical response to European history. Where borders are open to violent revision, insecurity becomes structural. States arm pre-emptively, alliances harden, minorities become hostages to geopolitical ambition, and war becomes self-justifying. The principle of territorial inviolability was designed precisely to end Europe’s thousand-year cycle of revisionist conflict.

That principle is now under direct challenge. The actions of Russia in Ukraine since 2014, culminating in the full-scale invasion of 2022, are not an isolated dispute over influence or alignment. They represent an explicit rejection of the post-war European settlement and a reversion to an older doctrine in which borders are contingent on military strength and historical narrative. The language used by the Kremlin, invoking medieval Rus, imperial inheritance and civilisational destiny, is itself a repudiation of modern European legal norms.

The danger for Europe lies not only in the specific case of Ukraine but in the precedent such actions create. If borders can be changed by force in one part of Europe, they can be challenged elsewhere. The continent’s political map contains numerous historical grievances and unresolved memories. Peace has endured not because these grievances vanished, but because force was delegitimised as a means of addressing them.

At the same time, Europe confronts a changing external environment. The strategic focus of the United States is increasingly global rather than Eurocentric. While Washington remains formally committed to European security through North Atlantic Treaty Organization, there is a growing uncertainty about the depth, duration and automaticity of American engagement. This uncertainty is not necessarily hostile, but it is structural. American resources and political attention are finite, and Europe can no longer assume that its security will always be the primary concern of a transatlantic partner whose strategic priorities extend from Latin America to the Indo-Pacific to the Middle East.

In this context the maintenance of the principle that borders shall not be changed by force cannot rely upon legal assertion alone. International law, in the absence of credible enforcement, becomes declaratory rather than constraining. Europe’s historical experience teaches that norms survive only when they are backed by power sufficient to deter their violation.

This leads to an uncomfortable but unavoidable conclusion. If Europe wishes to preserve the legal and political order that has underpinned her longest period of relative peace, she must be prepared to defend that order herself. This does not imply militarism or a rejection of diplomacy. Rather it recognises that diplomacy is effective only when supported by the credible possibility of resistance. Deterrence is not the antithesis of peace; in Europe’s history, it has been one of its necessary preconditions.

To be armed to whatever extent necessary is not to advocate uniform militarisation or reckless escalation. It is to accept strategic responsibility. Europe possesses the economic base, technological capacity and demographic resources to field armed forces capable of deterring territorial revisionism. What has often been lacking is not capability but political will and strategic coherence. The present moment, shaped by Russian aggression and American strategic recalibration, leaves little room for further ambiguity.

There is also a moral dimension. Smaller European states, particularly those on the continent’s eastern flank, depend upon the credibility of the border principle for their very existence. If Europe fails to defend that principle, she implicitly accepts a hierarchy of sovereignty in which some borders matter less than others. Such a hierarchy would fracture the European project and resurrect precisely the conditions that have historically led to war.

Europe’s thousand years of conflict do not suggest that borders are meaningless or eternally fluid. They demonstrate the opposite: that when borders are treated as provisional and enforceable only by strength, instability becomes endemic. The modern European commitment to territorial inviolability is not a naïve departure from history but its most hard-earned lesson.

In the absence of assured external protection, Europe faces a choice. She can either internalise that lesson and arm herself sufficiently to deter those who would redraw her map by force, or she can relearn, at great cost, why the lesson was written in the first place.