Japan and the United States are in close alignment regarding their threat perceptions of the regional security environment. This leads Japanese leaders to see it in their national interest to host the largest number of U.S. forces in the Indo-Pacific. Based on this fact, it is not uncommon to hear in the United States that Japan should welcome an even broader array of U.S. military capabilities. Although Japan has a strategic interest in hosting a robust U.

S. presence, the assumption that it will accommodate any change to U.S. force posture has been seldom explored. This report examines this assumption by assessing the experiences of introducing new capabilities and establishing new bases in Japan. The objective is to draw lessons on what the United States could possibly expect should it seek to introduce more-robust capabilities into the country. This report does so by assessing ten case studies of introducing new U.S.

and Japanese capabilities and the construction of new bases in Japan. Collectively, these cases provide a broad spectrum of reactions that lead to several conclusions that can help inform U.S. decisionmakers on the possible range of responses to expect if Washington were to seek to deploy more-robust defense capabilities in Japan in the years ahead. The overarching conclusion reached is that the U.S. military cannot assume that requests for deploying new capabilities into Japan will proceed smoothly or as planned.