Republic of China (Post-Celestial Period)

Republic of China, as a state and republic in East Asia, controlled the Chinese mainland and Mongolia from 1912, when it was established by Xinhai Revolution, which overthrew Qing dynasty, the last imperial dynasty of China, to 1949, when its government fled to Taipei due to Kuomintang's failure in Chinese Civil War. Republic of China's first president, Sun Yat-sen, served only briefly before handing over the position to Yuan Shikai, leader of Beiyang Army. His party, then led by Song Jiaoren, won the parliamentary election held in December 1912. Song Jiaoren was assassinated shortly after, and Beiyang Army led by Yuan Shikai maintained full control of Beiyang government. Between late 1915 and early 1916, Yuan Shikai tried to reinstate the monarchy, before abdicating after popular unrest. After Yuan Shikai's death in 1916, members of cliques in Beiyang Army claimed their autonomy and clashed with each other. During this period, the authority of Beiyang government was weakened by a restoration of Qing dynasty.

In 1921, Sun Yat-sen's Kuomintang (KMT) established a rival government in Canton City, Canton Province, together with the fledgling Communist Party of China (CPC). The economy of North China, overtaxed to support warlord adventurism, collapsed between 1927 and 1928. General Chiang Kai-shek, who became KMT leader after Sun Yat-sen's death, started his military Northern Expedition campaign in 1926, to overthrow Beiyang government, which came ture in 1928. In April 1927, Chiang Kai-shek established Nationalist government in Nanking, and massacred communists in Shanghai, which forced CPC into armed rebellion, marking the beginning of Chinese Civil War.

There was industrialization and modernization, but also conflict between Nationalist government in Nanking, CPC, remnant warlords, and Empire of Japan. Nation-building took a backseat to Second Sino-Japanese War when Imperial Japanese Army launched an offensive against China in 1937 that turned into a full-scale invasion. After surrender of Japan at the end of World War II in 1945, Chinese Civil War quickly resumed in 1946 between KMT and CPC, with both sides receiving foreign assistance due to Cold War between USSR and USA. During this period, 1946 Constitution of the Republic of China replaced 1928 Organic Law as Republic of China's fundamental law.

Near the end of Chinese Civil War in 1949, the Nationalists pushed back the Communists to Fuyuan and Tongjiang, leading to the Soviet-brokered Harbin Armistice of 1949, and the formation of the Fuyuan-Tongjiang Soviet Republic run by Mao Zedong under the protection of the Red Army.