chinese civil war
A civil war within China from 1921 to 1949. The war began after the collapse of the first Republic of China which saw the country being divided between various rival warlords who fought to unite the country. In 1927, the Kuomintang (KMT)-led Republic of China under the leadership of Chiang Kai-shek managed to unite a large part of the country, however, conflict between the then allied Chinese Communist Party (CCP) resulted in a crackdown that forced the CCP on "The Long March" to the northern parts of the country between 1934 - 1935. The outbreak of the Second Sino-Japanese war in 1937 forced the KMT and CCP to work together to defend the country.
After Japan was defeated in World War II in 1945, fighting between both parties resumed. While the KMT had a manpower and weaponry advantage, it was plagued with corruption and economical problems. Meanwhile, the smaller CCP forces used a combination of disciplined guerilla fighters, hit-and-run tactics, and various propaganda methods to recruit more members. After several key warlords and troops defected to the CCP, the KMT lost the control of the mainland China in 1949 and retreated to the island of Taiwan while the CCP established the People's Republic of China (PRC) over it.
As there is no official armistice, the civil war is still considered ongoing, with tensions between mainland China and Taiwan and its complex political status remains an issue.