Despite the initial plan of a unified Korea in the 1943 Cairo Declaration, escalating Cold War antagonism between the Soviet Union and the United States eventually led to the establishment of separate governments, each with its own ideology, leading to Korea's division into two political entities in 1948: North Korea and South Korea.
In the South Syngman Rhee, an opponent of communism, who had been backed and appointed by the United States as head of the provisional government, won the first presidential elections of the newly declared Republic of Korea in May. In the North, a former anti-Japanese guerrilla and communist activist, Kim Il-sung was appointed premier of the Democratic People's Republic of Korea in September. In October the Soviet Union declared Kim Il-sung's government as sovereign over both parts. The UN, which had a Western majority until 1955, declared Rhee's government as "a lawful government having effective control and jurisdiction over that part of Korea where the UN Temporary Commission on Korea was able to observe and consult" and the Government "based on elections which was observed by the Temporary Commission" in addition to a statement that "this is the only such government in Korea."[13] Both leaders began an authoritarian repression of their political opponents inside their region, seeking for a unification of Korea under their control. While South Korea's request for military support was denied by the United States, North Korea's military was heavily reinforced by the Soviet Union.