First United Front
In 1922, the KMT had formed the First United Front with the Communists to defeat the warlords and reunify China. In April 1927, however, Chiang split with the Communists and purged them from the Front against the wishes of the KMT leadership in Wuhan, setting up a rival KMT government in Nanjing. The split and the purge was detrimental to the KMT's Northern Expedition and allowed the Zhili-Fengtian coalition to launch a successful counterattack. The mostly leftist Wuhan faction soon purged the Communists as well and reunited with Chiang in Nanjing. The Northern Expedition restarted in February 1928 and successfully reunited China by the end of the year.