This book theoretically examines Japanese foreign policy and middle power diplomacy to suggest the country’s role as an international adapter middle power state, facilitating cooperation across ideological and systemic divides to comparative advantage within diplomatic entrepreneurship.

Drawing on more than three decades of fieldwork, interviews, and detailed case studies spanning security, trade, technology, development, and diplomacy, the author challenges the revisionism-and-militarism lens that has long dominated the study of Japanese foreign policy. Through a bold reconceptualization of Japan as an “international adapter state,” the book illustrates how Japan is able to exercise such relative outsized influence in the Indo-Pacific, while simultaneously revealing a pragmatic, inclusive, and adaptive actor invested in a rules-based order by situating the country within national, regional, and global contexts. The book details how Japan’s adaptive approach ultimately stems from structural constraints: a pacifist constitution limited by military options; a history of imperialism complicating regional leadership; and power asymmetries regarding the United States and China precluding hegemonic strategies.

The book will be of interest to scholars and postgraduate students in the fields of foreign policy, international relations and security, and Japan-US relations.