Assessing NATO’s cohesion: methods and implications

While united in initial responses to Putin’s aggression in Ukraine, NATO members face challenges as the alliance adapts to a significantly worsened security environment. Although Russia’s war in Ukraine provided NATO with a unifying threat, we argue that external factors are not sufficient to maintain its cohesion. This forum contribution develops a conceptual tool to assess alliance cohesion across both political and military dimensions, thus highlighting the agency of the “architects”, “bricoleurs”, and “agnostics” in shaping NATO’s internal politics. This approach allows for estimating the degree to which allies coordinate their political objectives, as well as the effectiveness of strategies to achieve them. To estimate the strength of alliance cohesion, we introduce four cohesion drivers—security threats, norms, institutions, and leadership—and assessment criteria. This article outlines three scenarios modelled on the war in Ukraine, suggesting that alliance cohesion suffers the most during prolonged security crises. Using this assessment tool can provide the “architects” of European security with ideas for policies aimed at strengthening NATO cohesion.