Allied Commitments and Public Support for Military Interventions: A Cross-National Experiment

Michal Smetana, Marek Vranka, Ondřej Rosendorf

Abstract: Recent survey experiments have found that the public in NATO countries is more supportive of intervening militarily on behalf of formal allies than non-allies. However, we lack empirical evidence on whether this effect of alliance treaties generalizes to non-NATO and non-Western publics. To fill this gap, we conducted a preregistered cross-national survey experiment on population samples (N = 7,200) in two Western NATO countries (the United States and the United Kingdom) and four non-Western regional powers (Russia, China, India, and Brazil). We show that while allied commitments shaped public support for military interventions in the pooled cross-national sample, their effect was significantly weaker in non-Western, non-NATO countries. Using a mediation analysis, we also found that feelings of moral obligation and the concerns about the reputational costs of non-intervention were similarly important mechanisms linking alliances to public support for honoring defense commitments. Our findings contribute to the scholarly debates on the microfoundations of collective defense and the generalizability of IR experiments beyond the Western context.

Keywords: Military Alliances, Collective Defense, NATO, Public Opinion, Survey Experiment, Cross-National Study