Strategic autonomy sounds compelling. However, building a European army would be far harder than Brussels admits.

For decades, the notion of a European army has hovered over Brussels like a political mirage. It reappears whenever the transatlantic relationship comes under strain, whenever Washington elects an administration less committed to European security, or whenever war erupts on the continent’s periphery. Russia’s invasion of Ukraine has once again transformed what was once an academic discussion into a serious policy debate.

Supporters argue that Europe can no longer afford to rely overwhelmingly on American military power. Critics counter that the idea of a unified European army remains less a strategic project than a political aspiration. Between these positions lies a difficult reality: creating a genuine European army would require a degree of political integration that many member states are neither willing nor able to accept.

The European Union already possesses many of the ingredients associated with military power. Combined defence spending among EU member states exceeds €300 billion annually. European countries field sophisticated armed forces, advanced aerospace industries and significant technological capabilities. Yet these assets remain fragmented across 27 nations, each with its own strategic culture, procurement systems, command structures and political priorities.

The attraction of a European army is obvious. Europe’s leaders increasingly speak of “strategic autonomy” — the ability to act independently when American interests diverge from those of Europe. Recent years have exposed uncomfortable truths. The war in Ukraine highlighted Europe’s dependence on US intelligence, logistics and military supplies. European governments have discovered that despite decades of rhetoric about defence cooperation, they remain heavily reliant on Washington for critical capabilities.

A truly integrated European force could, in theory, address these shortcomings. Duplication would be reduced. Procurement could be standardised. Instead of maintaining dozens of different weapons systems, Europe could concentrate resources on fewer platforms, generating substantial economies of scale. Military planners frequently note that Europe operates an extraordinary variety of tanks, aircraft and naval systems compared with the United States.

In practice, a European army would likely resemble a federal military structure rather than a collection of national forces. Recruitment might remain national, but operational command would shift to a central European headquarters. Procurement decisions could increasingly be made at EU level. Strategic planning would be coordinated across the bloc. National contingents might continue to exist, much as individual US states maintain National Guard units while ultimate military authority rests with Washington.

Such a transformation would undoubtedly enhance Europe’s ability to project power and respond rapidly to crises. It could create a more coherent deterrent against external threats. Smaller member states might benefit from access to capabilities they could never afford independently. Europe’s defence industry could become more competitive globally.

Yet the obstacles are immense.

The first challenge is political sovereignty. Defence remains one of the last bastions of national authority. Governments may happily coordinate environmental regulations or trade policy, but the decision to send citizens into combat touches the very essence of statehood. Would French troops accept being deployed under a command structure ultimately influenced by governments in Budapest or Bratislava? Would Poland permit decisions about its eastern border to be shaped by countries geographically distant from Russia?

These questions are not theoretical. They strike at the heart of democratic legitimacy. National governments answer directly to national electorates. A European army would inevitably raise difficult questions about accountability. Who decides when force is used? The European Commission? The European Parliament? The European Council? What happens when member states fundamentally disagree?

The second challenge concerns strategic culture. Europe is not strategically homogeneous. France has traditionally embraced military intervention and possesses nuclear weapons. Germany remains shaped by post-war caution. Eastern European states view Russia as the primary threat, while southern members often focus on instability in North Africa and migration across the Mediterranean.

A unified military requires unified strategic priorities. Europe currently lacks them.

The third challenge is NATO. Any discussion of a European army inevitably raises concerns about duplication. NATO already provides an integrated command structure backed by American military power. Critics argue that building parallel institutions risks wasting resources and creating confusion during crises.

Supporters respond that Europe must prepare for a future in which American commitments become less certain. Yet even they struggle to explain how a European army would coexist with NATO without generating overlapping bureaucracies and competing chains of command.

There is also a significant economic dimension. Establishing a genuine European military would require enormous investment. Standardising equipment, integrating command systems, creating common logistics networks and harmonising military doctrine would cost hundreds of billions of euros over many years. At a time when many governments are already struggling with ageing populations, rising debt and sluggish economic growth, political support for such spending cannot be assumed.

Perhaps the greatest obstacle, however, is public opinion. European citizens may support greater defence cooperation in principle, particularly in the wake of the Ukraine war. Support for a supranational military institution capable of deploying forces without direct national control is a very different proposition.

The debate ultimately reflects a broader question about the future of European integration. A European army is not merely a defence project. It is, by necessity, a political project. Successful armies serve states. They require common institutions, common interests and a shared sense of purpose.

Europe has made remarkable progress in economic and political integration over the past seven decades. Whether it possesses the political cohesion necessary to sustain a common military force remains far less certain.

For now, the vision of a European army remains exactly that: a vision. The more realistic path may lie in deeper defence cooperation, joint procurement and enhanced military interoperability rather than the creation of a single supranational force.

The dream of a European army appeals to those seeking a more autonomous and influential Europe. Yet dreams become reality only when politics, institutions and public consent move in the same direction. Europe has not reached that point. Indeed, it may be further away than many in Brussels care to admit.

Portugal: Nuno Melo draws red line on EU army ambitions as Spain pushes strategic autonomy debate