Long understudied by mainstream international relations (IR) scholars, the East Asian historical experience provides an enormous wealth of patterns and findings, which promise to enrich our IR theoretical literature largely derived from and knowledgeable about the Western experience. The intellectual contributions of this emerging scholarship have the potential to influence some of the most central questions in international relations: the nature of the state, the formation of state preferences, and the interplay between material and ideational factors. Researching historical East Asia provides an opportunity to seek out genuine comparisons of international systems and their foundational components. This introduction surveys the field and sets out to frame debate and the intellectual terms of inquiry to assess progress and guide future research. Theoretically, the essays in this issue provide insights on the emerging literature on hierarchy in international relations, and move beyond simplistic assertions that power “matters” to explore the interplay of material and ideational causal factors. Methodologically, scholars are no longer treating all East Asian history as simply one case, while also becoming more careful to avoid selection bias by avoiding choosing selective evidence from the rich historical record. Collectively, the empirical cases discussed in this volume span centuries of history, include a wide variety of political actors across East Asia, and represent an exciting wave of new scholarship.