Communist-controlled China (1927–1949)

The Chinese Communist Party (CCP) had sphere of influence zones within Republican era China from 1927 to 1949 during the Chinese Civil War, collectively called revolutionary base areas. They were also known as the Soviet Zone from 1927 to 1937 during the early stages of the Chinese Civil War, the Anti-Japanese Base Areas during the Second Sino-Japanese War, and the Liberated Zone during the final Stages of the Civil War from 1946 until the founding of the People's Republic of China in 1949.

There were six soviet areas from 1927 to 1933: the Jinggang Mountains, the Central Soviet in Eastern Jiangxi on the border of Fujian, the Eyuwan Soviet, Xiangexi (West Hubei and Hunan), and Xianggan (Hunan-Jiangxi). The first soviet was the Hailufeng Soviet created in 1927. The Central Soviet was the main base of the CCP where its leader Mao Zedong issued a directive on 1 September 1931 for the Central Soviet to mass mobilize the region as a base area. As problems occurred over being able to control territories outside the Central Soviet, by 1933 a full transfer of CCP forces to the Central Soviet was achieved. In 1931, the disconnected areas controlled by the CCP were declared the Chinese Soviet Republic (CSR).

Somewhat separately from the Chinese Soviets, there was a pro-Soviet Union protectorate ruled by Sheng Shicai following the Soviet invasion of Xinjiang. Sheng switched between alliance and hostility to the communists in the east.

Upon the intervention of the Soviet Union against Japan in World War II in 1945, USSR forces invaded the Japanese client state of Manchukuo. Mao Zedong in April and May 1945 had planned to mobilize 150,000 to 250,000 soldiers from across China to work with forces of the Soviet Union in capturing Manchuria. After the end of the war, the CCP controlled one-third of the territory of China. From 1945 to 1949, in the Chinese Communist Revolution, the CCP captured all Chinese territory except for Taiwan and several islands off the coast of Fujian, and established the People's Republic of China that exists today.