Most individuals realise that we have a moral obligation to avoid the evils of war. But this realization raises a host of difficult questions when we, as responsible individuals, witness harrowing injustices such as ""ethnic cleansing"" in Bosnia or starvation in Somalia. With millions of lives at stake, is war ever justified? And, if so, for what purpose? In this book, Richard J. Regan confronts these controversial questions by first considering the basic principles of just-war theory and then applying those principles to historical and ongoing conflicts. Part One presents two opposing viewpoints: first, that war is not subject to moral norms and, second, that war is never morally permissible. The author rejects both perspectives, and moves to define the principles of just-war theory. He evaluates the roles of the president, Congress and, most importantly, the UN Security Council in determining when long-term US military involvement is justified. The moral limits of war conduct and the moral problem of using, or threatening to use, nuclear weapons are also discussed. On the just cause to wage war, Regan argues that defense of nations and nationals - whether in self-defense or in defense of others - remains the ""only"" classical cause that in the modern world would justify resorting to war. With respect to military intervention in secessionist and revolutionary wars, he contends that such intervention might be justified, but that prudence dictates extreme caution. In considering acceptable war conduct, Regan elaborates the specific principle of discrimination and proportionality; he maintains that civilians uninvolved in the enemy's war should not be directly targeted and that the costs of military action must be proportionate to the anticipated benefits of destroying military targets. The second part of the book presents case studies of eight historical wars - World War I, the Vietnam War, the Falklands War, the revolution and civil war in Nicaragua, the civil war in El Salvador, the Gulf War, the intervention in Somalia, and the Bosnian War - and poses several provocative questions about each. It invites readers and students to apply just-war principles to complex war-related situations and to understand the factual contingencies involved in moral judgements about war decisions. The book should be of particular interest to students of the moral issues of international relations and to readers interested more generally in philosophy, theology and political science.