Amidst their other differences, the defeats suffered by the United States in Vietnam, Iran, and Lebanon have a common explanation. In all three cases American strategy was based on “global commitments theory.” Interests were to be defended and global credibility strengthened by the making, maintaining, reinforcing, and sustaining of American commitments to Third World allies. However, the core assumptions on which the logic of global commitments theory rests are plagued with inherent fallacies. These fallacies can be identified analytically as patterns of dysfunction along four dimensions of foreign policy: decision-making, diplomacy, military strategy, and domestic politics. They also can be shown empirically to have recurred across the Vietnam, Iran, and Lebanon cases. The central theoretical conclusion questions the fundamental validity of global commitments theory as it applies to the exercise of power and influence in the Third World. Important prescriptive implications for future American foreign policy are also discussed.