The Origins of the ROK-US Alliance’s Role in Deterring a “March to North” : Focusing on the 1948-1949 Military Executive Agreement and 38th Parallel Conflicts

This Study focuses on the early ROK-US military relations in 1948 1949 to identify the origins of the ROK-US Alliance’s role in deterring a “March to North.” Utilizing a tripartite analytical framework consisting of institution (agreements), space (the 38th parallel), and management actors (USFK), this study argues that the U.S. experience of failing to fully control the Syngman Rhee government’s unilateral offensives along the 38 parallel became the historic archetype for the post-war complex deterrence structure, which integrated the Armistice Regime (comprising the Armistice Agreement, the DMZ, and the UN Command) with the ROK-US Alliance. To this end, this study conducts an analysis of primary sources, including the Foreign Relations of the United States, the U.S. State Department’s 740.00119 Control(Korea) series, Records of General Headquarters, Far East Command, Supreme Commander Allied Powers, and United Nations Command, 1945 - 1960 (Record Group 554), the G-2 Weekly Summaries, and the Joint Weekly Analysis. Through these materials, this study reconstructs the multifaceted context of the strategic positions held by Washington’s high-ranking officials and local commanders such as John R. Hodge and Douglas MacArthur, the developmental patterns of the 38 parallel conflicts, and the transfer of Operational Control (OPCON) over the ROK Armed Forces across 1948, 1950, and 1954. The findings are as follows: First, the U.S. military preemptively secured OPCON over the ROK forces through the 1948 ROK-US Military Executive Agreement to prevent ROK offensives along the 38th parallel. Second, the subsequent loss of control following the USFK’s redeployment away from the 38th parallel caused the U.S. to re-evaluate the risks inherent in Korea’s autonomous military actions. Third, this experience served as the strategic background for MacArthur’s immediate demand for the assignment of OPCON upon the outbreak of the Korean War. Finally, in the post-war era, the U.S. took measures to establish a complex deterrence structure that coupled the ROK-US Alliance with the Armistice Regime as a practical tool to restrain the possibility of a ROK northward advance. This study is significant in that it challenges the conventional idea that views the ROK-US Alliance primarily as a defensive mechanism against North Korean aggression. Instead, it empirically demonstrates the attribute of “Northward restraint” inherent in the alliance since its formative period. In particular, it reveals how the pre-war conflicts along the 38th parallel were linked to the issue of ROK OPCON within the framework of the alliance.