Not so Intergovernmental After All? PESCO and Institutional Dynamics of emerging European Defence Cooperation

The expansion of European defence cooperation since 2016 has challenged long-held views of how integration develops within areas of traditional national sovereignty or core state power The Permanent Structured Cooperation (PESCO), the Coordinated Annual Review on Defence (CARD), and the European Defence Fund (EDF) have all combined to create a new model of defence capability development and defence-industrial coordination, which will significantly affect how future defence integration occurs and challanges earlier claims about the exlusion of supranational actors from high politics and overall strenght of integovernmental control mechanisms. However, at the same time, the continued use of unanimous decision-making, differentiated participation, and the continuing sensitivity of defence-industrial matters has led many observers to conclude that defence integration continues to be driven primarily member state-driven. Much recent academic work on emerging European defence cooperation has focused on either the formal institutional designs of these initiatives, the political bargains that occur during their implementation, or the evolving relationships between the EU and NATO. However, we still lack a systematic account of how PESCO operates in practice and how its organisational environment shapes the behaviour of participating states and by that extent also the emerging European defence ecosystem. Rather than treating PESCO as an isolated intergovernmental arrangement, this article conceptualises it as an open system, dependent on and embedded within a broader network of organisational, political, and technological actors. Applying an open-system perspective that draws on the organisational theory insights, allows us to reveal the structural interdependencies, porous boundaries, and competing institutional logics within PESCO. This highlights the importance of actors who are not part of the formal intergovernmental core, i.e., the European Defence Agency (EDA); the European External Action Service (EEAS) and its EU Military Staff (EUMS); the European Commission, (particularly DG DEFIS); and external organizations such as OCCAR — whose resources, expertise, management capabilities facilitate their influence. Thus, the presence of such actors limits the explanatory utility of purely intergovernmentalist accounts of defence integration. This article addresses the following research question: How do interdependencies, boundary spanning actors, and competing institutional logics condition the governance of PESCO as an open system? And what insights does this provide regarding the emerging European defence ecosystem? This article makes three contributions: a) theoretical: it provides a relational and organizational understanding of PESCO that refrains from being overly reliant upon supranationalist interpretations or overly reductionist in its intergovernmental account; b) empirical: it demonstrates that the governance of PESCO is dependent upon mediation, expertise translation, and managerial authority exercised across institutional boundaries; c) conceptual: it situates PESCO within a broader "European defence ecosystem," providing a structured explanation for why defence integration is accelerating while also being constrained.