In this history of South Korean foreign policy from the presidency of Syngman Rhee, who was in power from 1948 to 1960, through that of Park Geun-hye, who resigned last year, Snyder expertly describes the frustrations of a middle power that faces a persistent threat and depends on an inconsistent ally. Successive South Korean presidents have oscillated between attempts to punish North Korea and efforts to befriend it. The United States has also shifted between punitive and conciliatory approaches to Pyongyang, but it has often been out of sync with Seoul. Pyongyang has usually kept the initiative, shifting from provocations to talks and back again, always in search of concessions. Today, as well as mediating between Pyongyang and Washington, South Koreans are also debating how to balance a rising China against an unpredictable United States. Even though South Korea is one of the world’s richest and best-armed countries, autonomy remains frustratingly out of reach. If South Korea loses faith in the U.S. alliance, Snyder warns, it may well align with China.