History of Korea
After the end of WWII in 1945, the Allies divided the country into a northern area (protected by the Soviets) and a southern area protected (primarily by the United States). In 1948, when the powers failed to agree on the formation of a single government, this partition became the modern states of North and South Korea. The peninsula was divided at the 38th Parallel: the "Republic of Korea" was created in the south, with the backing of the US and Western Europe, and the "Democratic People's Republic of Korea" in the north, with the backing of the Soviets and the communist People's Republic of China. The new premier of North Korea, Kim il-Sung, launched the Korean War in 1950 in an attempt to reunify the country under Communist rule. After immense material and human destruction, the conflict ended with a cease-fire in 1953. The two nations officially remain at war because a peace treaty was never signed. In 1991, both states were accepted into the United Nations.
South Korea
Historically, Korea had close relations with the dynasties in China, and some Korean kingdoms were members of the Imperial Chinese tributary system. The Korean kingdoms also ruled over some Chinese kingdoms including the Kitan people and the Manchurians before the Qing dynasty and received tributes from them. In modern times, before the formation of South Korea, Korean independence fighters worked with Chinese soldiers during the Japanese occupation. However, after World War II, the People's Republic of China embraced Maoism while South Korea sought close relations with the United States. The PRC assisted North Korea with manpower and supplies during the Korean War, and in its aftermath the diplomatic relationship between South Korea and the PRC almost completely ceased. Relations thawed gradually and South Korea and the PRC re-established formal diplomatic relations on August 24, 1992. The two countries sought to improve bilateral relations and lifted the forty-year-old trade embargo, and South Korean–Chinese relations have improved steadily since 1992. The Republic of Korea broke off official relations with the Republic of China (Taiwan) upon gaining official relations with the People's Republic of China, which doesn't recognise Taiwan's sovereignty.