Recently many scholars in the history of science have been trying to illuminate why and how South Korea was able to achieve scientific and technological development simultaneously with economic growth. Scholars have focused on a top-down model led by the South Korean government and the role of technocrats who played crucial roles in the late 1960s. This study, however, focuses on the external conditions rather than on internal factors. U.S. policies towards South Korea became a major determinant of the development of science and technology during the Cold War, which brought about a number of important events such as the reorganization of the scientists’ society, the Minnesota Plan of the 1950s, establishment of the Korea Institute for Science and Technology (KIST) in 1966, and launching of the military industry in 1971. Transfers of advanced technology from Japan following the “normalization treaty” in 1965 also played a crucial role in developing both military and heavy chemical industries of South Korea in the 1970s. Ultimately, U.S. and Japanese policies led to rapid scientific and technological progress of South Korea, but at the same time limited the scale and direction of the development.