In recent weeks, it has become clear that all EU member states are preparing to ramp up military spending. This shift is driven both by the perceived threat from Russia and the expected disengagement of the United States from European affairs. Two key concerns have emerged among policymakers: How to finance this additional spending and how to address the long-standing fragmentation of European defence efforts. The second issue is particularly well known. Since the end of World War II, defence has largely remained the responsibility of individual states. As a result, European military spending is simply the sum of national budgets–an approach that is not only inefficient but also deeply fragmented. European security continues to rely heavily on NATO’s nuclear umbrella.

Fragmentation and foreign supply

The debate over funding is closely tied to the issue of fragmentation. The European Commission has proposed measures to foster collaborative projects within the defence industry and to promote joint procurement among member states. Yet early data from the period following Russia’s full-scale invasion of Ukraine in February 2022 suggests that fragmentation may be worsening. Some EU countries are increasingly turning to non-EU suppliers–particularly the United States and Israel–for their defence needs. As a result, the vision of a genuinely common European defence appears to be slipping further from reach.

Widening defence gaps

The rearmament of EU countries is raising serious concerns. One foreseeable consequence is growing inequality among member states. The gap between richer and poorer nations is becoming more visible. If security depends on military strength, then wealthier countries clearly have the upper hand. From this perspective, if security is truly a public good, it cannot be efficiently produced at the EU level without coordinated planning and fair burden-sharing. Otherwise, the divide between richer and poorer countries will widen, leaving some states less secure and more vulnerable.

Larger and wealthier nations–especially arms-producing countries such as France, Italy and Germany–stand to benefit disproportionately, while smaller, less affluent member states fall behind. Unless rearmament is accompanied by redistributive and compensatory reforms, the long-standing ambition of a common European defence will remain unfulfilled–and could become even less attainable.

Military spending and economy

Over time, higher defence spending could also undermine economic convergence within the EU. Not only will inequality between countries increase, but so too will inequality within them. Diverting resources to defence inevitably reduces funding for other public services–especially long-term investments that reduce inequality, such as education, healthcare and social protection. If the new military budgets are financed by rising public debt, the regressive effects on income distribution will be even greater.

Risks of deterrence logic

Against this backdrop of growing fragmentation and inequality, a critical question arises: Will the EU’s current rearmament efforts actually deliver the public good of security, or peace?

The prevailing strategy appears to be guided by deterrence, a concept rooted in Cold War logic. According to this approach, greater military strength enhances security: By increasing defence spending, a rational actor signals a credible threat to potential adversaries.

However, classic deterrence theory is static by nature. In non-cooperative game theory, actors choose fixed levels of military commitment, leading to a stable Nash equilibrium. While long dominant in international relations theory, this model oversimplifies the real-world dynamics of military build-up. In practice, increases in one state’s military investments often provoke similar moves from others–particularly non-allied states–triggering a spiral of escalation. This dynamic, known as an “arms race“, is inherently unstable.

Technological change and fragility

Rapid technological change further undermines the stability of deterrence. The spread of drone warfare and the potential military use of artificial intelligence are just two examples. According to some conflict models, even a perceived technological edge can raise the risk of escalation. Revisiting the insights of Thomas Schelling, it becomes clear that deterrence does not rest solely on weapons stockpiles. What matters more is a state’s credibility in its ability to respond and mobilise during a crisis.

In other words, the idea that amassing weapons automatically delivers deterrence is flawed–or at best, incomplete. Weapons are tools for building strategic credibility, which is a prerequisite for meaningful security. From this standpoint, the EU’s political fragmentation, lack of cohesion, and rising internal inequalities seriously weaken its strategic credibility in the eyes of Russia and other potential adversaries.

New security model

The current trajectory of EU rearmament raises urgent questions about the future of European security. If the true goal is to strengthen peace and collective safety, EU leaders must pursue a new approach–one that puts cohesion, fairness and strategic credibility above unchecked militarisation.