Book excerpt: During the premodern period, Japan had significant political, economic and cultural relations with Korea. This book purports that this period, from the fifteenth to the eighteenth century, was the formative stage of the East Asian diplomacy and ideology which laid the foundations for foreign relations between these two countries in the modern period. The book also investigates how Japan's and Korea's political and diplomatic ideologies emerged as a nascent form of nationalism which scholars have not previously clarified.