This volume examines the role of US alliances in the Asia Pacific, outlining their evolution and offering policy recommendations on how to adapt them to a changing regional security environment. To this end, a group of scholars and policymakers met at regular intervals over a three-year period to examine the alliances and the role they have played in shaping US engagement and the relationships among the alliance partners. While each alliance has its own history and each relationship has been shaped by events and circumstances, the system of bilateral alliances with the US has been a key part of the security architecture in the Asia-Pacific region for the past half century.