How do Americans decide whether their country should use military force abroad? We argue they combine dispositional preferences and ideas about the geopolitical situation. This article reports the results of a representative national survey that incorporated five experiments. Findings include the following: (1) Respondent dispositions, especially isolationism versus internationalism and assertiveness versus accommodativeness, consistently constrained policy preferences, whereas liberalism-conservatism did not; (2) features of the geopolitical context—the presence of U.S. interests, relative power, the images of the adversary's motivations, and judgments about cultural status—also influenced support for military intervention; and (3) systematic interactions emerged between dispositions and geopolitical context that shed light on when and why ideological disagreements about the use of force are likely to be amplified and attenuated by situational factors. Our results are consistent with a cognitive-interactionist perspective, in which people adapt broad predispositions in relatively thoughtful ways to specific foreign policy problems.