The alliance between the United States and South Korea arose from the postwar liberation of southern Korea by U.S. forces and then the subsequent attack on the newly independent country by North Korea, backed by the Soviet Union and Communist China, in June 1950. U.S. forces have remained in South Korea ever since, though their numbers have fluctuated over time.
During its first decades as an independent country, South Korea’s policy with regard to Pyongyang focused on being able to repel another North Korean invasion in partnership with the United States. The longer-term aspiration was to exploit the anticipated eventual collapse of the Democratic People’s Republic of Korea (DPRK), as North Korea is officially named, to reunify the Korean Peninsula under Seoul’s leadership, again with U.S. support.
North Korea never collapsed, but South Korea, despite its precarious security environment and limited natural resources, unexpectedly became an international economic superstar and achieved a global presence through the hard work and skills of its people. The transformation of South Korea, officially the Republic of Korea (ROK), into a liberal democracy helped further release these human resources. The ROK’s economic and political transition in turn made it a more valuable partner of the United States. Although security issues still dominate the U.S.-ROK alliance, their shared political values, robust economic exchanges and deepening human ties have provided a firmer foundation for the alliance, which would likely persist even after Korean reunification.