Violence and war were ubiquitous features of politics long before the emergence of the modern state system. Since the 1780s revolutions and terrorism have also challenged the idea of the state as a final arbiter of international order. This book covers ten major theorists of politics, violence and relations between states - Thucydides, Augustine, Machiavelli, Hobbes, Locke, Rousseau, Clausewitz, Lenin and Mao, and Schmitt. Each thinker is considered in detail, not just as a placeholder in 'realist' versus moralism debates.Conflict, war and revolution are generally seen in political thought as problems to be managed by stable domestic political communities. In different ways, all the paradigmatic thinkers here see them as inevitable dimensions of human experience, while yet manifested in different logics of acting politically and requiring different ways of handling. This book dramatically broadens the canon of political thought by considering perspectives on the international system that challenge its historical inevitability and triumph.