A distinguished historian explores how war has fundamentally shaped modern social and political order. Howard's sweeping narrative reveals the intricate relationships between warriors, capitalists, religious authority, intellectuals, state elites, and postwar order. Conflict does not just destroy orders, he argues, but defines and transforms them. War was once accepted as part of civilized life, whereas the notion that the international order should be peaceful is a relatively recent, Enlightenment invention. History also shows that peaceful orders are inherently difficult to build and easily destroyed. In the Napoleonic era, social change transformed the nature of war, whereas World War I transformed the nature of states and societies. Throughout the twentieth century, in fact, war strengthened and disciplined state authority, making states better able to uphold international order. But today the waning risks of major war, combined with globalization, appear to be eroding state authority. Howard then poses a vexing question: If states are needed to make peace as well as war, where does this leave today's international order? But he leaves others to look for answers.