Abstract
Existing literature suggests that alliance members can use their partners’ abandonment fears to obtain favorable concessions for themselves. However, evidence on the effectiveness of threats of abandonment as motivation for defense burden-sharing remains limited. This article uses a survey experiment conducted in Poland and Germany to assess how American signals of support and threats of abandonment shape public support for increasing their countries’ military spending. The findings suggest that threats of abandonment increase public support for higher defense spending, whereas approaches like “naming and shaming” under-contributing partners do not. However, assurances of protection did not decrease support for defense spending, and combining threats with assurances if anything increased those threats’ effects. Threats are thus most effective when they do not fundamentally undermine targets’ confidence in US protection. The findings have implications for understanding alliance politics and the utility of public pressure, and for policy debates about encouraging defense burden-sharing.