In Japan today, local or subnational governments (SNGs) together with many non-state organizations have joined national authorities to become important actors in international affairs. By comparison with SNGs in North America, western Europe and in some other countries, Japanese SNGs have been slow to extend their reach internationally. The rise of progressive mayors and governors in the 1960s and 1970s politicized some local issues that had a direct bearing on Japan’s foreign affairs. During the 1960s and 1970s, some SNG leaders involved their administrations in international relations simply by expressing opinion on critical issues such as war and peace and by making policies or pronouncements that were directly against Japan’s official position. This chapter also presents an overview of the key concepts discussed in the subsequent chapters of this book.