After the end of the war in the Pacific 2 September 1945, the Soviet and American forces occupied Korea. The Americans and Soviets could not agree on the election of a Korea government. As a result, Korea was divided along the 38th Parallel. The American government supported Syngman Rhee, the president of the Republic of Korea in the south. In the north, Kim Il Sung established the Democratic People’s Republic of Korea with Soviet support. While the Americans withdrew most of their forces from the Republic of Korea (South Korea), the Soviets heavily armed the Democratic People’s Republic of Korea (North Korea) and several Soviet military officers remained as advisors to the North Korea Army.
On 25 June 1950, the army of North Korea crossed the 38th parallel and invaded North Korea. The well-armed invasion force pushed the South Korean troops steadily southward. On 27 July, the United Nations Security Council passed a resolution calling for U.N. members to supply military assistance to the Republic of Korea (South Korea). The Soviet Union was a permanent member of the Security Council and had the power to veto any Security Council resolution. However, the Soviets had boycotted the Security Council because of its refusal to assign China’s permanent seat on the council to the new Communist Chinese government.
American troops began to arrive in South Korea 5 July 1950. Two days later, the United Nations appointed American General Douglas MacArthur as the commander of the UN forces in Korea.