Few, if any, events in modern history have had the instant, transformative impact of the terrorist attacks of September 11, 2001. In a matter of hours, the outlook of the United States changed profoundly. Gone were old beliefs about the almost unique security the nation enjoyed by virtue of its two ocean barriers to the east and the west and two friendly neighbors to the north and the south. Gone were broad confidences in the safety of critical systems such as commercial aviation. And gone was the assurance that terrorism, an age-old and familiar phenomenon, would be a tactic focused on the few. America's response to the cataclysm was broad based, with massive initiatives undertaken in the belief that the global security landscape, as well as key national institutions, needed reshaping to provide citizens with better security. The short essays in this volume offer evaluations by CSIS scholars of the progress and the setbacks to date in America's war on terror. They aspire to be both timely and balanced. Five years after the attacks, we have a basis for an initial consideration of how the nation has fared with the challenges that were set on that fateful day. It is the authors' hope that the judgments presented cast a light on this period that is both helpful and fair.