Many similarities exist between America's alliances with Japan and South Korea. The United States provides a security guarantee to both countries, and maintains a military presence in each. Local ambivalence about these foreign troops has long been a staple of politics in both countries. The two alliances are strategically connected. The United States would find it difficult to supports its commitments to South Korea without access to bases in Japan. Japan would have trouble sustaining political support for US Bases if it were America's only ally in the region. Trilateral security consultations among the United States, Japan, and South Korea enhance deterrence and generate diplomatic leverage with respect to North Korea. The US-Japan and US-ROK alliances have yielded mutual benefits for over fifty years. Yet today, while US-Japan defense cooperation is flourishing, conflicting perceptions in Washington and Seoul of Kim Jong-il's North Korean regime —and how to deal with it —have generated deep concerns about the future of the US-ROK alliance. This has prompted officials on both sides to shift their attention from managing these defense partnerships to redefining their terms. Armacost and Okimoto's provocative book examines this policy challenge. Substantial progress has been achieved in modernizing the US-Japan alliance. A shared US-ROK analysis of the North Korean challenge, and a common strategy for combating it, is now the urgent priority. Without it, the US-ROK alliance will not regain the relevance and promise that mark America's relationship with Japan. Given the stakes, Washington and Seoul must summon the political will to address current problems promptly and purposefully. Written by some of the most eminent scholars and practitioners in the field, the chapters in this timely volume offer thoughtful suggestions to help policymakers achieve this goal.