My book set out to answer one general and seemingly simple question: How did international relations function in East Asia from the fourteenth century to the nineteenth, before the arrival of the Western imperial powers?I make one overarching argument: that East Asian international relations exhibited two historical patterns, both of which were different from the European experience with the “balance of power.” The four main states of historical East Asia (Korea, Vietnam, Japan, and China) had generally stable and clear borders with each other and very little war. At the same time, the four states had endemic conflict with the various “nomadic” tribes and groups which existed along a vast frontier zone.In explaining this pattern, I argue that a set of international rules and institutions—known as the tribute system—governed the relations of the East Asian states during this time period.Emphasizing formal hierarchy and yet allowing considerable informal autonomy, Korea, Vietnam, Japan, and China had considerable peace and stability in their relations with each other. By contrast, the European “balance of power” system emphasized formal equality of nation-states, but entailed endemic conflict among states.Yet not all polities in East Asia played by the tribute system rules. The most fighting and problems occurred between these historical East Asian states and the nomads on their northern and western frontiers.The system comprised more than just war and diplomacy. Historical East Asia was also an economic international system, with extensive trade relations and cultural exchange among all the units in the region.China, the hegemon, was more than just a political power. From Siam to Java, to Vietnam, Taiwan, and even Japan, all the states traded with each other and particularly with China.It is common to use analogies from nineteenth century Europe—such as the rise of Bismarckian Germany—to explain East Asian relations in the twenty-first century. I hope this book contributes to viewing East Asia actually as a region of its own—with different states and distinct patterns, and not simply as a reflection of the Western experience.Today there is intense interest in whether these states can craft a stable relationship, especially with China’s emergence as an economic powerhouse. Given that they have centuries of history together, it is logical to ask how their relations worked in the past and whether this tells us anything about the present.