The United States has approximately thirty-seven thousand soldiers in South Korea—one of its largest standing deployments. Whether or not to withdraw these soldiers is one of the central debates regarding U.S. foreign policy in Asia.

The soldiers are a legacy of the Korean War, which was a surrogate battlefield of the cold war between the United States and the Soviet Union. Following World War II, Korea, which had been a Japanese colony, was divided along the 38th parallel into Soviet and American occupation zones. The temporary division of Korea became permanent when the former World War II allies could not agree on who would control a united Korea. This disagreement resulted in the creation of the Communist Democratic People’s Republic of Korea (DPRK) in the north, backed by the Soviet...