Abstract: How do US democratic allies perceive and adapt to the multiple challenges associated with the rise of multipolarity and the return of major war in Europe? This article examines how two US allies—Canada and Italy—have adapted their defense postures from the professed beginning of the shift in the balance of power in 2008 to Russia’s full-scale invasion of Ukraine in 2022. More specifically, it provides a comparison of three major dimensions of defense postures: threat perceptions, patterns of foreign military deployments, and military expenditures. This article argues that both allies have undertaken a shift from liberal interventionism towards a defense posture increasingly geared towards deterrence vis-à-vis Russia. However, the shift did not occur analogously and simultaneously, as the two allies’ adjustment was shaped by differing levels of domestic inter-party contestation. This article highlights the extent to which US allies’ international security adaptation follows political-party threat perceptions more than the traditional left-right dichotomy. Shared inter-party threat perceptions of great power revisionism are found to shape the degree of defense policy adaptation toward great power competition.
Keywords: Canada; defense posture; deterrence; foreign military deployments; Italy; liberal order; threat perception