The outbreak of ‘the war in Ukraine’ in 2022 has had impacts well beyond Europe, spreading throughout international society. This study reviewed the structural impact of the war on the global order, as well as on the regional order in East Asia. As a result, the study came to the following conclusions: First, rigidity in the international system is increasing, and regional blocs are gaining strength. Second, the U.S., having previously maintained regional security in Europe and Asia separately, is now seeking strategic change as Russia and China working closely together. Third, the U.S. is courting cooperation with its allies and partners by cementing stronger than-ever economic and military ties in East Asia. Simultaneously, South Korea faces both structural changes in the international order and North Korea’s nuclear threats. Against this backdrop, South Korea needs to pursue a principled and integrated security strategy, along with a flexible strategy compartmentalized into sectors to promote its security. Above all, South Korea needs internal balancing—including the strengthening of its security capabilities —while pursuing the development of innovative organizations. In external balancing, South Korea needs to make bold decisions and greater efforts by pursuing a global comprehensive strategic alliance with the U.S.