Do Foreign Military Deployments Provide Assurance? Unpacking the Micro-Mechanisms of Burden Sharing in Alliances

How do US foreign military deployments impact the defense policies of host states? Dominant scholarship holds that these deployments play a pivotal role in assuring allies that their security is guaranteed, which in turn leads host countries to neglect their national defense contributions. In this research note, we examine the micro-foundations of this conventional wisdom, investigating how nuclear and conventional troop deployments impact attitudes toward defense policies in (potential) host states. We highlight that the presumed linkage between assurance and free-riding critically implies that foreign military deployments must positively affect perceptions of security among host nations. We test this core logic, alongside some alternative pathways, at the micro level through two survey experiments that randomize hypothetical withdrawals (Germany) and deployments (Czech Republic). Although we find some evidence that foreign military deployments can decrease citizens’ subjective need for defense, the survey experiments also reveal that citizens hardly feel protected by these deployments. Thus, our results cast doubt on the core logic underlying the theory of free-riding in alliances.