This book examines how the current alliance between the United States and Japan might be redefined - and even restructured - to respond more effectively to the changing security environment in the region. Mike Mochizuki and Michael O'Hanlon of the Brookings Institution and Satoshi Morimoto and Takuma Takagashi from the Nomura Research Institute in Tokyo explore the critical factors of a successful U.S.-Japan security alliance. Their chapters are based on a series of intense discussions, as well as the views of Asian and American security and policy experts. The book analyzes the motivations, process, and results of both countries' official reviews of the current relationship; examines the strategic context of redefining the alliance, including the region's evolving security environment; and addresses ways to improve bilateral defense cooperation, including changes in the U.S. force structure in Japan. Finally, the authors make sweeping policy recommendations for strengthening the U.S.-Japan security relationship, increasing Japan's contribution to Asia-Pacific security, integrating China into the regional community, and reducing tensions on the Korean peninsula and across the Taiwan Strait.