Covering 1816–2016, this book deals extensively with the international system as well as the territorial outcomes of several key wars that were waged during that time period, providing an instructive lesson in diplomatic history and international relations among global powers. Based on an in-depth review of the leading theories in the field of international relations, International Relations Theory of War explains an innovative theory on the international system, developed by the author, that he applies comprehensively to a large number of case studies. The book argues that there is a unipolar system that represents a kind of innovation relative to other systemic theories. It further posits that unipolar systems will be less stable than bipolar systems and more stable than multipolar systems, providing new insights relative to other theories that argue that unipolar systems are the most stable ones. The first chapter is devoted to explaining the manner of action of the two dependent variables—systemic international outcome and intra-systemic international outcome. The second chapter presents the international relations theory of war and its key assumptions. The third chapter precisely defines the distribution of power in the system. The fourth chapter examines the theory's two key phenomena. The fifth and last chapter presents the book's conclusions by examining the theoretical assumptions of the international relations theory of war.