Conditional Assistance: Entrapment Concerns and Individual-Level Support for US Alliance Partners

Abstract In this paper, we explore how concerns about entrapment influence mass attitudes about armed support for an alliance partner. We focus on two separate dimensions of entrapment: allied crisis instigation and the risk of direct entanglement in a nuclear conflict. Our empirical analysis is based on US experimental survey data, collected in 2021. Our data analysis reveals two main findings. First, people are less likely to endorse military action in support of another country if that state is perceived as the instigator of a given military crisis. However, we find that allied crisis instigation only reduces individual-level support for certain types of military operations (cruise missile and nuclear strikes) but not others. Furthermore, even where significant, the substantive effect of our experimental vignette is fairly limited. This implies that US voters are not particularly sensitive to the potential for offensive entrapment in the US–South Korean alliance. Second, we find that nuclear deterrence threats from international rivals sap public support for military action. However, this is only true (1) for conventional military attacks and (2) if the US President does not provide a substantive justification for military intervention. As soon as leaders offer a detailed rationale for military action, the negative effect of foreign nuclear threats on support for the use of force disappears.