US foreign policy toward the Korean Peninsula cannot be understood without placing it in the context of US domestic politics and the broader context of US policy toward East Asia. This study explores the impact of US domestic politics on policy toward the Korean Peninsula between 1949 and 2000. Continuity characterized policy goals and military strategy, i.e. deterrence and collective security. Policy implementation, however, vacillated between containment (hard power) and engagement (soft power). Three major shifts are scrutinized: the Truman Administration’s approach to the Korean Peninsula before and during the Korean War, the Nixon Administration’s engagement of China, and the Reagan Administration’s initiation of engagement of the DPRK, a policy which the first Bush and Clinton Administrations continued. In each case, domestic political factors more than realities beyond the United States appear to have caused changes in policy implementation. This suggests that those wishing to promote US engagement of North Korea would do well to focus their effort on US domestic politics, particularly in the US Congress.