The Chinese Civil War was fought between the Kuomintang-led government of the Republic of China and forces of the Chinese Communist Party, with armed conflict continuing intermittently from 1 August 1927 until 7 December 1949, and ending with Communist control of mainland China.

The war is generally divided into two phases with an interlude: from August 1927 to 1937, the KMT–CCP Alliance collapsed during the Northern Expedition, and the Nationalists controlled most of China. From 1937 to 1945, hostilities were mostly put on hold as the Second United Front fought the Japanese invasion of China with eventual help from the Allies of World War II, but even then co-operation between the KMT and CCP was minimal and armed clashes between them were common. Exacerbating the divisions within China further was that a puppet government, sponsored by Japan and nominally led by Wang Jingwei, was set up to nominally govern the parts of China under Japanese occupation.

The civil war resumed as soon as it became apparent that the Japanese defeat was imminent, and the communists gained the upper hand in the second phase of the war from 1945 to 1949.

The Communists gained control of mainland China and established the People's Republic of China in 1949, forcing the leadership of the Republic of China to retreat to the island of Taiwan. Starting in the 1950s, a lasting political and military standoff between the two sides of the Taiwan Strait has ensued, with the ROC in Taiwan and the PRC in mainland China both claiming to be the legitimate government of all China. After the Second Taiwan Strait Crisis, both tacitly ceased fire in 1979; however, no armistice or peace treaty has ever been signed.