In the immediate aftermath of the catastrophes of September 11, it was easy to forget the earlier internal and transatlantic debate over how the United States should engage with the world. That debate, increasingly partisan and strident, raged during the previous decade and reached a crescendo after George W. Bush took office. When America’s vulnerability was revealed in September, the luxury of deciding whether, when, and how the United States should grant succor to others gave way before the compelling need to galvanize other countries to come to its aid. The United States appeared, uncustomarily, to be basking in the warm, near-unanimous embrace of multilateral and regional organs in which it had often found itself isolated and even scorned in the past. Not surprisingly, however, the preexisting clash of unilateral and multilateral perspectives, so far from having evaporated, reemerged, and members of both camps saw in the events of September 11 a vindication of their own past views and a prescription for the future.