The year 2004 marked the 150th anniversary of the signing of the first treaty of peace and amity (Treaty of Kanagawa) between the United States and Japan – a treaty which over time has both bloomed and failed, and falls into three phases, each lasting for a period of approximately fifty years. Phase one, which began in a context of force majeure but ended positively, lasted until the Russo-Japanese War of 1904-5; phase two began positively with the Treaty of Portsmouth which followed, but ended disastrously with the outbreak of the Pacific War; phase three began in 1952 with the San Francisco Peace Treaty and continues today. The author, who offers a significant Japanese view of the alliance as both a scholar and high-ranking military officer, explores the history, but also poses the question, what will be the relationship for the next fifty years. Through a close analysis of the nature of alliances, current issues and specific case studies, including the impact of a possible peaceful reunification of the Korean peninsula, he concludes that for the long-term stability of the Asia Pacific region, a continuing interdependent relationship between Japan and the US is a sine qua non. Fumio Ota is a Vice Admiral (ret’d) of the Japanese Naval Defense Forces, and until recently, was Director of Japan’s Defense Intelligence Headquarters.