<Li> Pork Chop Hill </Li> <Li> Korean Armistice Agreement </Li> <P> The Korean War (in South Korean Hangul: 한국 전쟁; Hanja: 韓國 戰爭; RR: Hanguk Jeonjaeng, "Korean War"; in North Korean Chosŏn'gŭl: 조국 해방 전쟁; Hancha: 祖國 解放 戰爭; MR: Choguk haebang chǒnjaeng, "Fatherland Liberation War"; 25 June 1950--27 July 1953) began when North Korea invaded South Korea . The United Nations, with the United States as the principal force, came to the aid of South Korea . China came to the aid of North Korea, and the Soviet Union gave some assistance . </P> <P> Korea was ruled by Imperial Japan from 1910 until the closing days of World War II . In August 1945, the Soviet Union declared war on Imperial Japan, as a result of an agreement with the United States, and liberated Korea north of the 38th parallel . U.S. forces subsequently moved into the south . By 1948, as a product of the Cold War between the Soviet Union and the United States, Korea was split into two regions, with separate governments . Both claimed to be the legitimate government of all of Korea, and neither accepted the border as permanent . The conflict escalated into open warfare when North Korean forces--supported by the Soviet Union and China--moved into the south on 25 June 1950 . On 27 June, the United Nations Security Council authorized the formation and dispatch of UN forces to Korea to repel what was recognized as a North Korean invasion . Twenty - one countries of the United Nations eventually contributed to the UN force, with the United States providing 88% of the UN's military personnel . </P>

Who were the main countries involved in the korean war