NATO and European security cooperation since the invasion of Ukraine

Abstract

The full-scale invasion of Ukraine by Russia in February 2022 represented a watershed moment for European security and prompted a significant reassessment of NATO’s strategic posture. This dissertation examines how NATO’s approach to European security shifted in response to the invasion, tracing the evolution of its strategy across the years 2022, 2023, and 2024. It investigates the nature and scale of this shift by analysing rhetorical changes, tangible military and strategic developments, and transformations in security cooperation, both externally with the European Union and Indo-Pacific partners, and internally among NATO member states. Employing a qualitative, inductive research methodology and thematic analysis, this study draws upon primary sources such as summit declarations, official communiqués, member state speeches, and NATO strategic documents, complemented by a wide range of scholarly analysis. It follows a structured empirical framework that allows for a year-by-year analysis that highlights the evolution of key strategic themes. The literature review situates the study within ongoing scholarly debates about NATO enlargement, European deterrence, and the adequacy of NATO’s response both after the 2014 annexation of Crimea and the 2022 invasion. The findings reveal that NATO underwent a multidimensional transformation from a crisismanagement orientation to a more structured model rooted in deterrence, forward defence, and strategic integration. Key indicators of this shift include the codification of Russia as the most direct threat to Euro-Atlantic security, the reinforcement of NATO’s eastern flank through expanded high-readiness deployments, record-high defence spending across many member states, large-scale military exercises on European soil, and the institutionalization of support for Ukraine. The creation of new frameworks such as the NATO-Ukraine Council and the NATO Security Assistance and Training for Ukraine (NSATU) initiative, coupled with increasingly coordinated NATO-EU engagement, reinforced this transformation. However, the research also identifies growing political divergence among member states. While frontline states such as Poland and the Baltics remained vocal advocates for continued support to Ukraine, others, including Hungary and Slovakia, resisted deeper engagement and called for negotiated settlements. The re-election of Donald Trump in the United States in late 2024 further intensified uncertainty about the future of NATO cohesion and transatlantic reliability. This dissertation concludes that NATO’s post-2022 approach marks a historic departure from its previous trajectory and reflects a credible, if uneven, strategic realignment. Yet, the sustainability of this shift remains uncertain. It will depend not only on military readiness but also on the alliance’s ability to preserve internal unity and maintain a common vision for European security amid shifting political dynamics and escalating global competition.