The United States frequently reassures allies of its protection by stationing troops abroad, visiting allied countries, and making public statements. Yet the causes of reassurance in asymmetric alliances – those between a great power patron and its weaker allies – are understudied in the academic literature. Indeed, many scholars argue that reassurance can be counterproductive as it invites allies to free-ride or provoke their adversaries, knowing that they have their patron’s support. Despite the drawbacks, I argue that the United States use reassurance to discourage their allies from seeking outside options and reducing their dependence on the alliance. Patrons like the United States thus face a dilemma wherein they trade off between withholding reassurance for short-term leverage and using reassurance to preserve their long-term influence. I test the theory using a new cross-national dataset of U.S. statements of reassurance from 1950-2010, and the results provide stronger support for my hypotheses than for the competing explanations of deterrence, strength from desperation, and shared preferences. The findings have implications for understanding how great powers manage their alliances, and suggest a pathway through which weaker states can shape great powers’ foreign commitments.

中文翻译：

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压力下的承诺：美国同盟的保证声明

美国经常通过派兵到国外，访问盟国并发表公开声明来确保盟国得到保护。然而，学术文献中并未充分研究不对称联盟中让人放心的原因-大国资助者与其较弱盟友之间的关系。的确，许多学者认为，放心可能会适得其反，因为它邀请盟友知道自己得到赞助者的支持而搭便车或挑衅对手。尽管存在种种弊端，但我认为，美国还是可以放心地阻止其盟友寻求外部选择并减少对联盟的依赖。因此，像美国这样的赞助人面临着一个两难选择：在为短期杠杆作用而扣留保证金与保持长期影响力之间进行权衡。我使用1950-2010年间美国放心声明的新的跨国数据集对该理论进行了检验，结果为我的假设提供了有力的支持，而不是对威慑，绝望的力量和共同的偏爱的竞争性解释。这些发现对于理解大国如何管理其联盟具有暗示意义，并为弱国建立大国的外国承诺提供了一条途径。