Much recent U.S. strategic thinking about Asia has focused on China or the prospect of a nuclear-armed North Korea. These concerns have overshadowed important changes in Japan that have been influenced in part by developments in those two countries. Transformation in Japan, changes occurring elsewhere in the region, and in the U.S. itself, add entirely new meaning to former U.S. Ambassador Mike Mansfield’s mantra, “the Japan-U.S. relationship is the most important bilateral relationship, bar none.”