China officially became communist on Oct. 1, 1949 after years of internal conflict when Mao Zedong proclaimed it the People's Republic of China. As chairman of the Chinese Communist Party, Mao Zedong, often called Chairman Mao, became the ruler of China until he died in 1976.
When the Communists were victorious, Chiang Kai-Shek led the opposition Nationalist party to Taiwan, where they set up a government in exile. The United States broke relations with mainland China and worked with Taiwan as if it were the legitimate government of all China. Until President Richard Nixon reopened diplomatic ties with mainland China, the United States continued this policy, even endorsing Taiwan's occupation of China's United Nations seat.