The emergence of the European Security and Defense Policy (ESDP) in the last two-thirds of the 1990s and continuing into the new century, has been a complex process intertwining politics, economics, national cultures, and numerous institutions. This book provides an essential background for understanding how security issues as between NATO and the European Union are being posed for the early part of the 21st century, including the new circumstances following the terrorist attacks in New York and Washington on September 11, 2001. This study should be of interest to those interested in the evolution of U.S.-European relations, especially in, but not limited to, the security field; the development of institutional relationships; and key choices that lie ahead in regard to these critical arrangements.