By 1927, the differences between the Nationalists and Communists in terms of beliefs and goals for China was so great that the Chinese Civil War erupted. The Communists received some aid from the Soviet Union but were vastly outgunned by the Kuomintang and the armies of the warlords allied with them.

The Chinese Communists had several things going for them. Firstly, unlike the Kuomintang, they were seen as free from foreign influence and corruption. Secondly, they operated in secret cells, which made destroying the Communists almost impossible. Third, the Communists operated in the countryside. For the most part, they were peasants hiding among peasants, with goals similar to the people around them. Fourth, after some hard lessons, the Communists began to carry out a guerrilla war, striking suddenly and retreating before a response could be coordinated. Lastly, the Communists had an appealing philosophy that was combined with really effective propaganda. The Chinese Communist beliefs called for rule from the bottom-up, rather than the top-down, to put it simply. Instead of slow reforms as the Nationalists preached, the Communists called for the immediate overthrow and eradication of the landlord class, and in the areas under their control in the countryside, they did just that.

By 1931, China was a divided country. War existed in fits and starts between the Communists and the Nationalists, the foreigners controlled much of the economy, and what central government did exist was forced to compromise with largely corrupt warlords who controlled their own private armies, some of them quite large. China, at this point, was not a strong country and became something of a target, and it was in 1931 that Japan decided to act against China, something that they had been planning for quite some time.

Between 1975 and 1976, the internal power struggles divided the CCP, and Mao largely let the sides continue their feuding. It is possible that he knew that if they went after each other, they would not be able to attack him. The problem was that this undermined the progress that Zhou Enlai and Deng Xiaoping had made to fix the problems caused by the Cultural Revolution. By the end of 1975, the Gang of Four would finally take the control they felt they deserved.