Abstract Following Russia's annexation of Crimea in 2014 and the ensuing civil war in eastern Ukraine, NATO has gradually refocused on collective defence. The incremental form of this transformation has been due in large part to NATO's internal dynamics, a delicate balance having had to be found repeatedly over the past decade between political and military considerations as well as among NATO allies' varied perspectives. To shed light on these internal dynamics, this article conceptualizes the politics of allied war planning along two dimensions: a vertical dimension, reflecting the challenge of aligning political ends and military means, and a horizontal dimension, capturing the need to forge common ground among allies. Through this lens, the article examines NATO's renewed emphasis on collective defence, with an empirical focus on the transformation of the alliance's conceptual apparatus—the strategies, military concepts and defence plans that have provided the intellectual coordinates for its evolving deterrence and defence posture. By analysing these milestones, the article contributes to a better understanding of NATO's pivot back towards collective defence as well as to the discussion on NATO's adaptation. It highlights the alliance's endurance, which can be attributed not only to the strength of its institutions but also to its ability to handle internal tensions, on both a politico-military and an inter-allied level, around its core mission: preparing allies to fight together.
Elie Perot (2025) studied this question.