This book is based on a multinational and multidisciplinary discussion between American and European researchers and practitioners on the moral, legal and political dilemmas raised by the use of force in today's world. Are humanitarian interventions and counter-terrorism just forms of war in disguise? Is the just war tradition still relevant? What role does the issue of legitimacy play in the actions of states? Does the notion of "the global war against terror" play into the hands of terrorists? What are the lessons of the recent military interventions, from Kosovo to Iraq? What role for the U.N., for international criminal justice? What consequences for international order? The book provides no definitive answers but is the clearest and most searching book available to students and to the general public.