<P> With the onset of the Cold War, negotiations between the United States and the Soviet Union failed to lead to an independent and unified Korea . In 1948, UN-supervised elections were held in the US - occupied south only . Syngman Rhee won the election while Kim Il - sung was appointed as the leader of North Korea . This led to the establishment of the Republic of Korea in South Korea, which was promptly followed by the establishment of the Democratic People's Republic of Korea in North Korea . The United States supported the South, the Soviet Union supported the North, and each government claimed sovereignty over the whole Korean peninsula . </P> <P> The subsequent Korean War, which lasted from 1950 to 1953, ended with a stalemate and has left the two Koreas separated by the Korean Demilitarized Zone (DMZ) up to the present day . </P> <P> When the Russo - Japanese War ended in 1905 Korea became a nominal protectorate of Japan, and was annexed by Japan in 1910 . The Korean Emperor Gojong was removed . In the following decades, nationalist and radical groups emerged, mostly in exile, to struggle for independence . Divergent in their outlooks and approaches, these groups failed to unite in one national movement . The Korean Provisional Government in China failed to obtain widespread recognition . </P> <P> In November 1943, Franklin Roosevelt, Winston Churchill and Chiang Kai - shek met at the Cairo Conference to discuss what should happen to Japan's colonies, and agreed that Japan should lose all the territories it had conquered by force . In the declaration after this conference, Korea was mentioned for the first time . The three powers declared that they were, "mindful of the enslavement of the people of Korea,...determined that in due course Korea shall become free and independent ." Roosevelt floated the idea of a trusteeship over Korea, but did not obtain agreement from the other powers . Roosevelt raised the idea with Joseph Stalin at the Tehran Conference in November 1943 and the Yalta Conference in February 1945 . Stalin did not disagree, but advocated that the period of trusteeship be short . </P>

Approximately where was the border set between north korea and south korea at the time