The Korean War: Invasion, Inchon, and Chinese Intervention (1950)

The proclamation of the People's Republic of China in October 1949 and the Soviet Union's first atomic bomb test that same year emboldened Kim Il-sung and Stalin's confidence that a Korean offensive could succeed without direct American resistance. Kim Il-sung traveled to Moscow and Beijing in 1949 and 1950 seeking backing for reunification by force; Stalin conditioned his approval on a guarantee of Chinese support in case of American intervention, and Mao Zedong agreed to back the operation, calculating the United States would not intervene directly. In January 1950, Secretary of State Dean Acheson delivered a speech that explicitly excluded Korea from the American "defensive perimeter" in Asia, a statement later interpreted as a possible green light for invasion, while the withdrawal of most American troops from the south in 1949 had already left it militarily weakened.