Alfred T. Mahan’s Geopolitical Threat Perception and Thought of Foreign Policy and Changes on U.S. Foreign Policy in the Early 20th Century

China’s rapid rise since the 2010s threatens a global hegemony of the United States, which seemed to become a permanent superpower after the post-Cold War following the collapse of the Soviet Union. Just like the United States at the beginning of the 20th century, China is building an aggressive foreign policy and a strong naval force to support it. The U.S. is also making various efforts to counter the rise of China and to deter the challenge of hegemony. The U.S. efforts and grand strategic origins in the Asia- Pacific region were the geopolitical threat perception and foreign policy theory of Alfred T. Mahan, one of America’s leading maritime geopolitical scholars and maritime strategists. Although the specific form and method have changed little by little according to the changes of the times, it is true that the actual grand strategic essence has not changed significantly in the early 20th century or in the modern era beyond the 2020s. Therefore, the Republic of Korea, which takes the R.O.K-U.S. alliance as the basis of national security, should pay attention to Mahan's perception of geopolitical threat and foreign policy theory in its historical essence in order to accurately and soberly recognize the grand strategic origins of U.S. foreign policy. Through this, we will be able to get a little closer to what the fundamental grand strategic origins of the U.S. are and what their essence is, beyond the simple recognition of the current status quo of the U.S. foreign policy.