Strategic issues and crises in foreign policy are usually managed by relatively small groups of elite policymakers and their closest advisors. Since the pioneering work of Irving Janis in the early 1970s, we have known that the interplay between the members of these groups can have a profound and, indeed, at times a pernicious influence on the content and quality of foreign policy decisions. Janis argued that "groupthink," a term he used to describe...