As shocking as the attacks of 9/11 were, it would be wrong to view the post-9/11 struggle against terrorism as entirely new. Without denying certain novel aspects of Al Qaeda and its affiliates, the "newness" of its purpose and methods has been overemphasised. Many aspects of contemporary terrorism bear a striking resemblance to past movements. Others represent the culmination of trends evolving over decades. Even seemingly novel characteristics of terrorist methods may be more the outcome of earlier developments than a truly new phenomenon. The increased lethality of terrorist attacks is a case in point. Usually attributed to lack of restraint brought on by religious extremism, the emphasis on body count may owe as much to a threshold phenomenon. Numbed by decades of violence, people do not shock as easily as they once did. It now takes thousands of deaths to produce the same effect once caused by a relative handful. This book examines the nature of the contemporary threat within a historical context to discern continuities and change in terrorist behaviour. It challenges the idea of a global war on terrorism and suggests that the United States, or any threatened country, would be better served by a policy aimed at reducing the risk of terrorist attack to an acceptable level at a reasonable cost. The book concludes by proposing a workable strategy for achieving this reasonable level of security.