After ruled by Japan, the Korean War (25 June 1950 – 27 July 1953) had happened between South Korea and North Korea. South Korea was supported by the United Nations and North Korea was supported by China and the Soviet Union. The war was terribly continued till 1953 and both sides had suffered heavy casualties as follows. South North
Dead 178,426 367,283-750,282
Wounded 566,434 686,500-789,000
Apparently, this war broke out because political border between North and South Korea tensed and it deepened the division; the North established a communist government, while the South established a right-wing government. However, Kim Il-sung was determined to achieve reunification with the South Korea by force. The underlying reason is America and Russia were using it to fight without Hot War. By supporting South Korea, America tended to fight Communism without directly attacking Russia. For Russia, Stalin wanted to grow Communism through uniting the Korean Peninsula under communism.
America and its allies agreed to help defend South Korea with the support of the UN as they don’t want communists to extend their ideology into South Korea and Japan further. UN troops used Pusan as their base and captured Inchon and Seoul. When America participated in the war, South Korea only maintained a small territory. They decided to land at the city of Inchon which is very close to Seoul and 38th parallel. The location had been criticized as too risky, but UN Supreme Commander Douglas MacArthur insisted on carrying out the landing. By the early evening, the Marines had overcome moderate resistance and secured Inchon. The brilliant landing cut the North Korean forces in two, and America with UN force pushed inland to recapture Seoul that had fallen to the communists in June. Allied forces then converged from the north and the south, devastating the North Korean army and taking 125,000 enemy troops prisoner.