A crucial element of South Korea's security has been its alliance with the United States. The alliance was formalized in 1953 with the signing of a mutual defense treaty, but the relationship began informally when World War II came to an end. The alliance has had its high and low points, as all long-term relationships do. What began as a patron–client relationship between Washington and Seoul is evolving into one that resembles more of a partnership, although an unequal one. The alliance has been the subject of a multitude of studies in the past fifty years, and the precise nature and future of the alliance remain unknown. It appears likely that the alliance, although shifting in form, will remain an important part of South Korean security and the overall security architecture in East Asia for some time. This chapter will examine the history and components of the alliance, the efforts begun under the George W. Bush administration to restructure the U.S. force presence, and the future direction of the alliance.

An Uncertain Guarantee: 1945–1953

Prior to World War II, Korean ties with the United States were minimal, but the closing days of World War II brought Korea to the attention of U.S. leaders. With Japan's hasty surrender after the dropping of the atomic bombs, U.S. officials quickly crafted a proposal for the United States and the Soviet Union to divide the peninsula at the 38th parallel for taking the Japanese surrender.