This book argues that terrorism in the modern world has occurred in four "waves" of forty years each. It offers evidence-based explanations of terrorism, national identity, and political legitimacy by leading scholars from various disciplines with contrasting perspectives on political violence. Whether violence is local or global, it tends to be both patterned and innovative. It elicits chaos, but can be understood by the application of new models or theories, depending upon the methods and data experts employ. The contributors in this volume apply their experiences and studies of...