China has a record of at least one major upheaval each decade of the 20th century: 1900s: Anti-foreign Boxer Revolt sweeps across China in 1900.
1910s: Revolution topples the Qing dynasty in 1911. The subsequent republic is weakened by the 1919 May 4 Movement - demonstrations fired by anti-Japanese nationalism and demands for modernization and democracy.
1920s: Nationalist Kuomintang, led by Chiang Kai-shek, gradually assumes power. Nationalist forces massacre thousands of communists in 1927.
1930s: Communists complete Long March from south China to far northwest, followed in 1937 by war between China and invading Japanese forces. Japanese massacre thousands in 1937.
1940s: After Japan's defeat in 1945, civil war breaks out between Nationalists and Communists. Communist victor Mao Zedong proclaims People's Republic in 1949.
1950s: Mao launches widespread anti-rightist purges and executions, followed by Great Leap Forward, a production drive which reorganizes agriculture into people's communes.
1960s: Mao announces Cultural Revolution in 1966, launching 10 years of turmoil.
1970s: After Mao's death in 1976 and the elevation two years later of Deng Xiaoping as China's preeminent leader, the party introduces sweeping economic reforms which permit private farming, a measure of free enterprise, and opening to the outside world. Deng balks at substantial political liberalization.
1980s: Student demonstrations for democracy in 1986 lead to the downfall in 1987 of reformist Communist Party chief Hu Yaobang. His death April 15, 1989, triggers current protests.