Testing Tripwire Theory Using Survey Experiments

Many scholars and policymakers assume that attacks on forward deployed U.S. troops—“tripwires”—will prompt strong domestic political support for escalation against the attacker. This conjecture informs policy and has deep theoretical roots, yet it is undertheorized and largely untested. We identify and develop two theoretical mechanisms – reputation and revenge – capable of explaining why such attacks might prompt support for escalation, even though prior research shows that casualties suffered during a conflict reduce support for intervention. We then use two survey experiments to examine whether and how attacks influence Americans’ support for intervention. We find that hypothetical attacks on contingents of troops deployed overseas increase support for escalation only modestly and in ways that better reflect demands for revenge rather than concerns about reputation. Our findings imply that confident assessments that forward deployed troops serve as strong pre-commitment devices need to be tempered, pending further theoretical and empirical analysis.