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.

中文翻译：

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外国军事部署是否提供保证？解读联盟中责任分担的微观机制


美国的外国军事部署如何影响东道国的国防政策？主流学术认为，这些部署在确保盟友的安全得到保障方面发挥着关键作用，这反过来又导致东道国忽视其国防贡献。在本研究报告中，我们研究了这一传统智慧的微观基础，研究了核能和常规部队部署如何影响（潜在）东道国对国防政策的态度。我们强调，保证和搭便车之间的假定联系关键地意味着外国军事部署必须对东道国的安全观念产生积极影响。我们通过两个随机化假设撤军（德国）和部署（捷克共和国）的调查实验，在微观层面上测试了这一核心逻辑以及一些替代途径。尽管我们发现一些证据表明外国军事部署可以减少公民的主观防御需求，但调查实验还表明，公民几乎没有感受到这些部署的保护。因此，我们的结果对联盟搭便车理论的核心逻辑提出了质疑。