North and South Korea was split in August 1945 at the end of World War II. The country was divided at the 38th parallel, with the Soviet Union controlling the north and the United States controlling the south. Tensions on how to unite the two regions would lead to the Korean War.
At the end of World War II, the Japanese surrendered to the Soviet Union in Korea north of the 38th parallel and to the U.S. south of the 38th parallel. Part of the agreement was to allow Korea to reunite and become reestablished as an independent country. However, the communist Democratic People's Republic of Korea and capitalist Republic of Korea were both formed in 1948. The political differences of the two lead to the Korean War. The end of the war in 1953 created the buffer known as the Demilitarized Zone.