Whether economic interdependence is a cause of war or peace constitutes a central debate in international politics. Two major approaches advance diametrically opposed claims: liberal theory holds that interdependence between states promotes peace by increasing the costs of war; realist theory argues that interdependence is just another word for vulnerability, a condition that states may try to escape by seizing the resources and markets they need for self-sufficiency. Considerable evidence supports both of these claims. In Economic Interdependence and War, Dale Copeland proposes to resolve this stalemate by showing that interdependence promotes peace when states expect mutually beneficial trade to continue, but creates incentives for war when at least one of the states expects that trade trends will leave it dangerously vulnerable. Notwithstanding this book's major theoretical contributions and its impressive historical research, it leaves open several important questions about how to move forward with its agenda of theoretical development and testing.