The national identity of the Korean people is the result of shared experiences during Korea’s modern and contemporary history. In this regard, anticommunism, which greatly influenced society following the birth of the Republic of Korea, was closely related to the identity of the Republic of Korea. In general, the national identity tends to be identified with ethnic identity. In the case of Korea, which found itself under the unique environment characterized by the division of the nation into two Koreas, the identity of the political system has greatly influenced the formation of the national identity. This study focuses on the formation of the identity of the political system, and in particular on the anticommunism that is regarded as having exercised the greatest influence on the formation of the identity of the political system. Previous studies have exhibited a tendency to overemphasize the negative impact which anticommunism had on liberal democratic values and political development, while overlooking a periodic situation that was characterized by the advent of the Cold War order and the uniqueness of the North-South Korean relationship. Anticommunism, which is based on communal principles, has in some ways had a negative impact on liberal democracy, under which individual freedom is regarded as being of great importance. However, viewed from the standpoint of national security, anticommunism ironically can also be regarded as having served as a bulwark that protected liberal democracy. The Republic of Korea could not have achieved its current levels of economic prosperity and political democratization if it had not served as an anticommunism bulwark that protected its system from the political attacks of the communists. Consequently, it was inevitable for the Republic of Korea, which found itself confronted by North Korea, to opt for the ‘necessary evil’ of anticommunism.