This book explores the essential nature of regionalism by conducting a comprehensive analysis of more than 30 regionalist proposals made by Japan and other Asian countries throughout the post-war period. Shintaro Hamanaka examines the whole post war period and covers all regionalist proposals since then, while most existing studies cover only the development of Asian regionalism in the recent decade. A significant number of cases in the proposed book enable the readers to go beyond an understanding of each regionalist project, to a deeper understanding of theoretically generalizeable behavior pattern of Japan and other countries. The book also comparatively analyzes political, financial and trade regionalisms. The central aim of the book is to reveal the fact that policies with regard to regionalism have a pattern, in this case with a principal, though not an exclusive focus, on Japan. The author demonstrates that the behavior pattern of external policy is extremely consistent in terms of the membership of regionalist organizations and discusses whether this new approach to regionalism holds explanatory power vis-à-vis regionalism outside Asia.This book will be of interest to scholars, postgraduate students and policy makers in the fields of international relations, Asian studies, international trade and regionalism.