The Qing dynasty which had ruled China for centuries had gone weak by the beginning of the twentieth century. The dynasty tried to modernise the country, but the efforts did not go well. In 1911, the Chinese Revolution (also known as Xinhai Revolution) took place, which ended the 2000 year old imperial rule in China.
After a series of unstable governments, there arose a major split in the Kuomintang nationalist party and the Communist Party of China. As the country was already in trouble, the Kuomintang party’s position had not been impressive. Thus, the Communist party started attacking and taking control of the land.
The communists particularly gathered the attention of the peasants, women and the working class, who were previously oppressed by the nationalist party. The Kuomintang only turned weaker with time while the communists grew stronger. The civil war only came to an end in 1949, when Mao Zedong led Communist Party took the complete power. Although, some might say that the civil war is not completely over, it has just been suppressed by a powerful regime.