In the last decade, US foreign policy has been in a period of transition, as ideas and institutions have begun to adapt to the demands of the new international system. In retrospect, it is clear that the 1990s represent the latest in a series of 20th-century moments of transition in US foreign relations, in which, as after both of the world wars, old consensus assumptions were abandoned and debate ensued over the broad outlines of the nation’s appropriate world role in the future. Over time, centrists among US foreign policy elites have forged a new consensus, which balances the liberal internationalism of the early Clinton administration with the conservative internationalism of some of its critics and takes historical lessons from an understanding of Vietnam as well as World War II and the Cold War. To an even greater extent, however, it is driven by commonly perceived lessons from the more recent US interventions in Bosnia and Kosovo, and now the terrorist attacks on US soil. These historical frames will create the cognitive backdrop, the common set of expectations and assumptions, for US foreign policy elites in the years ahead.