Theorising inter-organisational relations: the "EU-NATO relationship" as a catalytic case study

This article explores the historical evolution of research on the "European Union (EU)-North Atlantic Treaty Organisation (NATO) relationship" since the 1950s and examines the numerous ways in which it has served as an important case study for applying and developing theory-guided and conceptual research on inter-organisational relations (IOR) in International Relations. After a dearth of policy-oriented research during the 1990s and early 2000s, a wide range of scholars have contributed to a "conceptual turn" in the study of EU-NATO during the last decade. This development, as this article will argue, not only signifies a stronger interest by scholars to understand the complex relationship between both organisations with the help of more theory-driven research, but also highlights that the EU-NATO relationship has become a "catalytic case study" in terms of inspiring conceptual experimentation and advancing efforts to theorise IOR more generally. The article provides for the first time a systematic stock-taking and analysis of the richness of concepts and theoretical debates related to EU-NATO relations research and offers scholars wider insights into the most promising approaches and analytical tools for understanding and theorising EU-NATO relations.