Sovereignty vs. Security

European Army: Opportunities and Hurdles

Introduction

Against the backdrop of ever-increasing global military conflicts like the war in Ukraine to escalating tensions in Iran, the European Union’s defense capabilities are becoming increasingly more of an issue. In particular, the question is how the European Union positions itself militarily as an independent player within NATO. Furthermore, a fully-fledged European army could simplify military logistics and also create economic synergies among individual EU member states with regard to defense budgets. In addition, a fully integrated force would enable more efficient training and the harmonization of regulations, command structures, and other specific aspects of the individual armed forces, thereby creating a more effective military force. Historically, there have already been several attempts and conceptual discussions regarding the idea of a European army.

The quest for the sovereignty of European defence and the subsequent legal evolution of the intergovernmental Common Foreign and Security Policy (CFSP) are rooted in the early, ambitious attempts at integration during the 1950s. A primary milestone was the Treaty instituting a European Defence Community (EDC), signed by the six founding members of the European Coal and Steel Community (ECSC). This project, which aimed to create a supranational European army, was ultimately abandoned in 1954 following the French National Assembly’s refusal to ratify the treaty. This failure created a profound shift in the integration process; questions surrounding external action and communal defence became politically taboo, remaining largely untouched for nearly two decades. This silence was finally broken by the Davignon Report of 1970, which established the European Political Cooperation (EPC). Crucially, the EPC operated outside the formal Community framework, utilizing an intergovernmental method that allowed Member States to coordinate foreign policy without ceding sovereign powers to supranational institutions. The legal consolidation of this practice occurred in 1986 with the Single European Act (SEA). Through Article 30 of the SEA, the dispositions relating to the European Political Cooperation that had developed throughout the 1970s were formally codified. However, this legal framework was notably limited: it concerned only questions of political and economic security, explicitly excluding military or defence concerns. Despite these limitations, the SEA set the critical legal and political precedent for the formal creation of the intergovernmental CFSP pillar by the Maastricht Treaty of 1992, marking the transition from informal cooperation to a constitutionalized European foreign policy.

Legal Hurdles

The European Union was not originally conceived as a defense alliance like NATO, but rather as an economic union. The close ties fostered by open borders and a common currency are based on this concept, while the idea of merging national armies into a single European army has so far remained merely a theoretical possibility. Because of its original conception as an economic union, the transformation into a common defense alliance faces legal hurdles.

Article 42 of the Treaty on European Union (TEU) is the legal cornerstone of the EU's Common Security and Defence Policy. In principle, the common defense policy is also an integral part of the European Union, Art. 42(1) TEU. In accordance with Article 42(7) of the TEU, member states are generally obligated to provide any assistance and support within their power to a member state that is the victim of an armed aggression on their territory. While this provision mirrors the collective defence logic of Article 5 of the NATO Treaty, it is materially weaker in practice; its operation on a purely intergovernmental basis grants each Member State a broad discretion in determining the nature of their response. This flexibility is particularly significant given that several Member States (notably Ireland, Austria, Malta) maintain traditions of military neutrality, which therefore dilutes the operative force of the mutual assistance clause. The article also indirectly emphasizes national sovereignty in the area of defense policy in its second sentence. This mechanism is illustrated by the first-ever invocation of the provision. Following the terrorist attacks of November 13, 2015, France decided to invoke Article 42(7) rather than resort to the EU solidarity clause of Art. 222 TFEU or Article 5 of the NATO Treaty. This allowed France to bypass EU institutions and cooperate directly with individual Member States, with a focus on bilateral military support. However, Article 42(2) merely establishes a declaration of intent to gradually define a common defense policy for the Union. This is intended to lead to a common defense only once the European Council has unanimously decided to do so. Unanimity thus represents not only a legal hurdle but also a practical one, which complicates the implementation of this idea. This is particularly true at the present time, when some states are calling for less regulation by the EU rather than an expansion of the EU’s powers. Furthermore, in most EU member states, an amendment to the national constitution would likely be necessary to transfer such competence in the area of defense to the European Union, which further complicates the process.

Legal Solution

The legal hurdles identified above are significant, but they are not immovable. The history of European integration itself is a history of legal obstacles overcome through political will, institutional creativity, and incremental adaptation. The question here is not whether a path to deeper European defence integration exists, but which path, or combination of paths, is most viable given the political, legal, and strategic landscape of the European Union. Three principle options merit examination; formal treaty amendment, enhanced cooperation among willing Member States, and the continued expansion of the EU’s rapid deployment capacity within the existing treaty framework.

A formal treaty amendment under article 48 TEU would ultimately be the most direct route to a fully integrated European Defence. This article provides access to an ordinary and simplified procedure for altering the foundational EU treaties. This pathway would grant the Union an express competence in territorial defence, by establishing a supranational command structure (contrary to the current intergovernmental method), and provide a legal basis for a European Defence Union, or European Army. The European Parliament’s 2023 report on treaty reform proposed precisely this ambition - including the creation of a European Defence Union with genuine institutional oversight. However, the political viability of this route remains highly uncertain. Thirteen national governments responded to the European Parliament’s proposal by publishing opinions that rejected the treaty changes deeming them “premature”, signaling the hurdle at the very heart of this debate; the strong reluctance among Member States to cede national sovereignty in the defence domain. This reluctance is reflected in the Treaty of Maastricht (1992), in which it led to the establishment of CFSP as a separate and intergovernmental pillar, deliberately excluded from the supranational community method. This institutional choice, deliberately preserved through the treaties Amsterdam (1997), Nice (2001), and even Lisbon 2009 (where the pillar structure was abolished), maintained the intergovernmental character of the CFSP, highlighting a consistent and deeply held resistance among Member States to the communitarisation of defence competence. This resistance is consistent with historical precedent; the treaty revision process has typically required between 3 to 8 years to complete, and have systematically been derailed by negative consensus in national ratification procedures. Denmark’s initial rejection of the 1992 Maastricht Treaty, Ireland’s rejection of the 2001 Nice Treaty as well as the 2009 Lisbon Treaty, and the French and Dutch rejection of the 2005 Constitutional Treaty, all convey the fragility of this process. Moreover, as Steven Blockmans concluded in the ‘European Defence Project of Common Interest’ study, the defence reform timeline which targets meaningful change by 2030 is “too short to add territorial defence to the Union’s mandate and reform the EU institutional setup through treaty change”. Treaty amendment therefore remains the only avenue for foundational change, but its feasibility in the short to medium term is nullified by the severe constraints of both political will and procedural complexity.

Practical Solution

Given the practical limitations of treaty reform, the most plausible path forward within the existing legal framework is the expansion of the EU’s rapid deployment capacity (RDC). Described by the European Parliament itself as a “de facto mini EU army”, the RDC represents a pragmatic approach to defence by building operational capability without requiring the transfer of defence competence to the Union’s community competence. As of 2025, the RDC is operational and capable of deploying up to 5000 soldiers under EU command via the Military Planning and Conduct Capability (MPCC). While the number of soldiers it is capable of deploying may seem disappointing, its significance lies in the precedent it establishes; for the first time, multinational MS forces operate under coordinated EU operational oversight, even as individual soldiers remain under national sovereignty. In 2023, proposals were put forward to expand the RDC to a force of up to 60,000 troops, with the goal of functioning as a 28th army, complementary to the national forces of the Member States. This model draws primarily on Permanent Structured Cooperation (PESCO) initiatives, which provide a legal mechanism under articles 42(6) TEU and and 46 TEU for willing Member States to deepen military integration on a voluntary basis, without requiring unanimity among all 27 of them. The RDC pathway therefore offers a critical advantage; it advances European defence integration incrementally, while respecting the sovereignty concerns that have consistently blocked more ambitious reform. In this sense, the RDC functions not merely as a gap-filler, but as a potential foundation upon which deeper integration could gradually be constructed, by promoting political trust and an operational track record that may, in time, make treaty-level reform more achievable.

Conclusion

The establishment of a fully integrated European army remains, for now, a legal and political impossibility. The intergovernmental architecture of the Common Foreign and Security Policy, the unanimity requirements embedded in Articles 42(2) and 48 TEU, and the consistent reluctance of Member States to cede defence sovereignty (demonstrated repeatedly from the failure of the EDC in 1954 to the thirteen governments that rejected treaty reform as “premature” in 2023), collectively prevent any prospect of foundational change within this area in the short and medium term. Treaty amendments remain the only route to a genuine European Defence Union, but it is a route that will remain unexplored without the political conditions necessary to travel it.

Yet the geopolitical landscape demands progress that cannot wait for treaty revision. The war in Ukraine and escalating tensions in the middle east as well as across the EU’s neighbourhood have made the case for autonomous European defence capability not merely theoretical, but urgent. In this context, the Rapid Deployment Capacity represents the most viable path forward; not as a substitute for deeper integration, but as a precursor. The building of an operational track record under coordinated EU command, expanding multinational interoperability through PESCO, and gradually extending the scale of deployable forces, the RDC can serve as the institutional and political foundation upon which future treaty-level reform may one day be constructed. The path to a European army, if it is to be found, will not be built in a single legislative act, but incrementally through demonstrated capability, political trust, and the accumulation of shared operational experience.

Given the geopolitical risks, the debate over the possibility of a European army is a very timely one. Even though legal obstacles currently exist, it would theoretically be possible to remove them by amending the treaties. However, this would require unanimity. A more pragmatic solution could therefore be a “light” European army, which would function more as a rapid reaction force or a special operations unit.