This year marks the 70th anniversary of the Korean Armistice Agreement and the subsequent signing of the ROK-U.S. Mutual Defense Treaty. For the past seventy years, the ROK-U.S. alliance has been a critical framework for South Korea's security. But why did South Korea actively pursue a bilateral security pact rather than a multilateral alliance similar to NATO? To answer this question, it is helpful to briefly review South Korea's geopolitical calculations during the Korean War.