abstract: Counterinsurgency (COIN) is a long process that even great powers struggle with. Nevertheless, South Korea as a middle power was successful with COINs in Vietnam and Iraq. What were the drivers for the Republic of Korea (ROK) military's success? This dissertation maintains that the unusual nature of missions coupled with political/socio-cultural advantages are sufficient conditions for success of the middle power COIN. COIN missions are seen as unusual to middle powers. A rare mission stimulates military forces to fight harder because they recognize this mission as an opportunity to increase their national prestige. COIN mission success is also more probable for middle powers because their forces make the best of their country's political/socio-cultural advantages. The ROK military's COINs are optimal cases to test these hypotheses. The ROK military's COIN in Vietnam was an extremely rare mission, which increased its enthusiasm. This enthusiasm was converted into appropriate capabilities. By identifying battleground dynamics, the ROK forces initially chose an enemy-oriented approach based upon the method of company-led tactical base, and then later introduced a population-led method. South Korea's political/socio-cultural advantages also contributed to its military success in Vietnam. The Confucius culture that South Koreans and Vietnamese shared allowed the ROK forces to win the hearts and minds of the Vietnamese population. The mission in Iraq was also a rare and important one for national prestige. Accordingly, South Korean forces were equipped with pride and were enthusiastic about missions in Arbil. They changed their organization from a rigid one to a more flexible one by strengthening civil-military units. The ROK military possessed the ability to choose a population-centric approach. South Korea's political and cultural climate also served as an advantage to accomplish COIN in Iraq. The culture of Jung allowed ROK soldiers to sincerely help the local Iraqis. This project contributes to developing a theory of the middle power COIN. The findings also generate security policy implications of how to deal with contingent situations led by the collapse of the North Korean regime and how to redefine the ROK military strategy for the future. / Dissertation/Thesis / Ph.D. Political Science 2011