Defense treaties increase domestic support for military action and casualty tolerance: Evidence from survey experiments in the United States

ABSTRACT Do security guarantees affect people's willingness to spend their country's “blood and treasure” in a military crisis? Recent research finds that international legal commitments reshape domestic policy preferences. However, the focus of that scholarship is traditionally on issues such as human rights that define a society's normative obligations. In this study, we deploy two original survey experiments in the United States describing a potential military crisis on the Korean peninsula. We find that increasing the salience of the 1953 agreement between Washington and Seoul increases support for military action and that individuals become both more tolerant of U.S. military deaths and North Korean civilian casualties. In addition, the breadth of these effects increases when individuals are provided more detail about the agreement. These results extend the analysis of international law and domestic preferences into the domain of national security politics.