How NATO Membership Transforms Public Support for War

Abstract

How do military alliances affect public support for defending targets of aggression? We explore this question in the context of current debates about NATO expansion. We fielded an experiment on 14,000 voters in 13 NATO member-states involving a hypothetical scenario in which Russia attacked a target country, and we randomly varied whether the target was a member of NATO. Contrary to the view of alliances as empty gestures, we found that voters in every country were far more willing to use military force to defend each target when the target was in NATO. We also uncovered important heterogeneity across targets and within domestic audiences. These findings have profound implications for understanding the effects of alliances in general, and debates and rhetoric surrounding NATO in particular.