Presidents George Bush and Bill Clinton have made the promotion of democracy abroad the "third pillar" of their administrations' foreign policy. In his 1995 National Security Strategy, President Clinton states that "All of American Strategic interests....are served by enlarging the community of democratic and free nations." However, the theory underpinning this strategy is not well developed. In fact, the policy directly conflicts with the realist analytical framework that dominates current international diplomacy. Recent empirical studies in international relations have confirmed the statistical evidence of a separate peace among democratic nations. Few militarized disputes, and perhaps no wars have occurred between democracies. However, the causes of this phenomenon remain controversial. Up until now, efforts to explain the democratic peace phenomena have focused on the existence of domestic norms and institutions within democracies. Hegemonic stability theory provides insight for a new plausible explanation of the democratic peace proposition. Statistical analyses of interstate dispute data indicate that two centuries of liberal hegemony have, at least partially, been responsible for the separate democratic peace. This finding represents an important contribution to the international relations literature and has significant implications for United States national security policy.