This thesis examines the activities of the anti-Communist guerrilla unit on the west coast during the Korean War, particularly based on the primary resources produced and collected by the British Royal Navy. The purpose of this study is to present a very significant, but not been studied enough on their co-operation with the Western UN Naval Forces. For this purpose, this thesis seeks to explore the beginning and development of UN naval and the guerrilla unit co-operation system during the first one year of the war. As the naval-guerrilla unit relationship was initially started from mid-December 1950, and was able to be settled down in July 1951, to understand the guerrilla's role in the conduction of the UN naval operation, it is important to focus more on the early part of the Korean War. This thesis shows that, to the Western Naval Forces, working with the irregular groups was operationally essential to the conduct of the naval blockade mission, and this naval-guerrilla relationship was of major factors during their naval campaign in Korea.