It has become a truism to say that the US-Japan alliance has been the cornerstone of peace and security in the Asia-Pacific region since the end of World War II. By providing the forward bases for nearly 40,000 US troops over a period of half a century, Japan has allowed United States to maintain a permanent presence in a region thousands of miles away from the American homeland. This role became even more important from a geostrategic standpoint when the United States lost its southern bases in the Philippines in the early 1990s. Since then, the alliance has struggled to adapt to the post-Cold War world and the rise of China. In this period, both the US and Japan have looked to embed the relationship in the larger dynamic of Asian interstate relations. This process will continue as long as the United States maintains its regional security commitments and as long as China continues to reshape the regional security environment.