How have analysts assessed NATO expansion as a cause of the Ukraine war compared to other explanations?
Executive summary
Analysts are divided: a substantial school argues NATO’s eastward expansion created the security fears that helped precipitate Russia’s 2022 invasion, a competing school emphasizes Russian agency, imperial ambition, and domestic politics as primary drivers, and a third cluster offers a nuanced, multi-causal synthesis that places NATO expansion as one important contributing factor among several structural and proximate causes [1] [2] [3]. The debate is as much about competing interpretive frames — Kremlin grievance versus Western sovereignty and deterrence — as it is about discrete causal mechanisms, and competing agendas on all sides shape which explanation is emphasized [4] [5].
1. Historical warnings: who said expansion would provoke Moscow
Prominent realist critics and former officials long warned that pushing NATO toward Russia’s borders would predictably inflame Kremlin insecurity; commentators and former policymakers like Robert Gates and long-standing realist voices argued that expansion — and efforts to bring Georgia and Ukraine into NATO — risked provoking Moscow and were mismanaged after the Soviet collapse [1]. These warnings were public and persistent in the 1990s and 2000s and are cited by those who view the 2022 invasion as a foreseeable consequence of Western policy choices [6].
2. The Kremlin’s grievance and explicit demands
Moscow’s own framing tied its use of force explicitly to NATO’s trajectory: Russian leaders and negotiators demanded freezes or rollbacks of NATO enlargement in diplomatic ultimatums leading up to the war, and cited expansion and perceived broken promises as central grievances used to justify aggression to domestic and international audiences [7] [3]. Those Kremlin claims function both as a political pretext and as a straightforward reflection of how Russian authorities portrayed their security calculus [2].
3. Analysts who treat NATO expansion as a primary cause
Scholars and commentators who treat expansion as causally central point to the cumulative effect of bringing former Soviet-space countries into a military alliance, NATO’s growing military ties with Ukraine, and the 2008 Bucharest language promising eventual NATO membership as key triggers that altered Moscow’s threat perception and helped move it toward coercive measures [2] [1] [4]. That argument emphasizes deterrence failure and humiliation narratives: if states previously within Russia’s sphere now join a rival military bloc, Moscow’s strategic compulsions to prevent loss of influence can lead to military action [1].
4. Analysts who reject NATO enlargement as the main cause
A countervailing literature insists NATO expansion cannot absolve Russian responsibility and underscores Putin’s agency, imperial ambitions, and domestic politics, noting that Russia invaded and annexed Crimea in 2014 and pursued policies independent of Western offers or denials [3] [8]. Other analysts emphasize structural drivers beyond alliance politics — energy dependencies, authoritarian consolidation, and geopolitical ambitions — arguing that those factors better explain Russian behavior and that portraying NATO as primary risks exculpating Moscow [5].
5. Nuanced, multi-causal accounts and policy implications
A growing body of scholarship and policy analysis treats NATO expansion as one significant variable interacting with others: historical grievances, NATO’s force posture and support to Ukraine, Russian revanchism, and changing domestic politics within Russia, producing a complex causal web rather than a single smoking gun [9] [10]. Policy pieces from Western institutes argue that while NATO enlargement contributed to Kremlin insecurity, policymakers must balance deterrence and reassurance and cannot treat NATO as the sole lever for preventing Russian aggression; failing to recognize multiple drivers risks simplistic solutions [11] [12].
6. Verdict: relative weight, uncertainty, and political uses of the causation debate
Most serious analysts converge on a qualified answer: NATO expansion was a meaningful and foreseeable contributor to Russian threat perceptions and thus a proximate factor in the crisis, but it did not deterministically cause the invasion — Kremlin decisions, domestic politics, and imperial objectives were independent and decisive drivers of Putin’s 2014 and 2022 choices [2] [3] [1]. Disagreements often reflect differing normative commitments (realist restraint versus liberal support for sovereign choice) and geopolitical agendas — Russia, China, and some Western critics all use the NATO-expansion frame to advance competing strategic narratives — so cause attribution remains contested and politically freighted [4] [5].