This report examines the relationship between U.S. casualties and public support for U.S. military intervention in Korea and Vietnam, and concludes that a strong inverse relationship existed between the two. It also assesses to what extent concern over adverse public reaction to U.S. casualties and the resulting decline in public support influenced presidential decisionmaking with respect to military intervention in Vietnam, overriding purely strategic or military considerations. The research approach consisted primarily of interviews with senior Johnson Administration officials. It concludes that (1) limited wars often cost more and last longer than anticipated, (2) public support inevitably declines with mounting casualties, no matter what interests are at stake, and (3) democracies can't continue fighting limited wars indefinitely with steadily declining public support. It recommends that minimizing U.S. casualties should be a central objective in the formulation of new strategies, force configurations, and weapon systems for limited war contingencies.