The purpose of this paper is to identify the nature of the stay of two divisions of the US Armed Forces in Korea immediately after the Korean War. In other words, the study stemmed from a question on whether the political decision, namely the stay of the two divisions of the US Armed Forces in Korea, was the maximum involvement of the USA or whether the USA tried to minimize their involvement in the national defense of Korea. With this aim, this paper tried to obtain an answer to the research question through a detailed analysis of the following facts. First, the paper looks into the trend of global strategies of the USA immediately after World War II from a macroscopic perspective. This is to discover relevant factors at a national level for the USA, as a rational actor, to prefer involvement in or withdrawal from the Asian region. Second, the paper reviews in detail other selected-to-be sites that were mentioned, except for the stay of the two divisions, through the policy making process of the USA from a microscopic perspective. This is indispensible to see in detail the nature of the level of involvement implied by the scale of two divisions. Third, in order to analyze more accurately such macroscopic·microscopic trends, the paper carried out an analysis of the case of the representative military policy making of the USA immediately after World War II, diachronically. The conclusions from the analysis include the following. First, keeping two divisions in Korea immediately after the Korean War was made from a propensity of involvement, which was done at the time when the need for US involvement in Asia was being augmented. Second, this was the optimal selection for the USA in realizing the greatest goals back then, namely the enhancement of the need for security under the Eisenhower Administration and the achievement of a financial balance, that is, it was the maximum involvement that the USA could undertake for Korea while satisfying both foreign and domestic demands. Also, through this the following are the conclusions as theoretical implications. First, it is difficult to understand comprehensively a specific fact only either from a microscopic analysis at a fragmental national level or a microscopic analysis at a policy making process level. Second, preferences at a national level defined ultimately the direction of diplomatic policy, and any difference in degree is determined more in detail within such a basic direction through the policy making process. Finally, the relevace of all related models to the policy making process can be confirmed once again.