Republic of China (1912–1949)

The Republic of China (ROC) was a country that existed between 1912 and 1949. It is now the People's Republic of China. It was created in January 1912 after the Xinhai Revolution, which overthrew the Qing dynasty. The Republic's first president was Sun Yat-sen. Sun's party, the Kuomintang (KMT) won the parliamentary election in December 1912. 
But Sun soon gave the position to Yuan Shikai, the leader of the Beiyang Army. The Beiyang Army also controlled the Beiyang government (which controlled Mongolia). 
Between late 1915 and early 1916, Yuan Shikai called himself the Emperor of China. But people did not like it (National protection war). 
After Yuan died in 1916, the Beiyang government was further weakened by a brief restoration of the Qing dynasty. Various groups in the Beiyang Army claimed independence and fought with each other during the Warlord Era.
In 1921, the KMT created a rival government in Canton, supported by the Communist Party of China (CPC). 
North China was overtaxed and had too many fighting warlords. So its economy died between 1927 and 1928. 
General Jiang Jieshi (Chiang Kai-Shek) became the KMT leader after Sun's death. Jiang started the Northern Expedition in 1926 and overthrew the Beiyang government in 1928. In April 1927, Jiang created a nationalist government in Nanjing and massacred Communists in Shanghai. This forced the CPC into armed rebellion, starting the Chinese Civil War.
China experienced industrialization and modernization but suffered conflicts between the Nationalist government in Nanking, the CPC, warlords, and the Empire of Japan. 
Eventually the Chinese unified to fight against their common enemy: the Japanese. In 1937 the Imperial Japanese Army invaded China in 1937. The Second Sino-Japanese War began.
In 1945 Japan surrendered at the end of World War II.
In 1946, the Chinese Civil War between the KMT and CPC restarted. 
In 1949, the CPC defeated the KMT and started the People's Republic of China (PRC).
Jiang Jieshi and the KMT fled to Taiwan.