Sun Yat-sen sought Soviet support for the reunification efforts. Mikhail Borodin, an agent for the Comintern (Communist International), an organization promoting world communism, conferred with Sun in 1923. Together, they created the First United Front. The First United Front was an alliance between the Kuomintang (KMT) and the Communist Party of China (CPC). The CPC had been founded in 1921 and was quickly growing in popularity.

Sun Yat-sen's vision was to develop a reunified China according to three phases: 1) reunion of China by force, 2) politically-based education in the new government, and 3) introduction of democracy. In 1925, Sun died, and Chiang Kai-shek took over the reins. He created a military arm to support the Kuomintang, the National Revolutionary Army.

The CCP joined the KMT as individuals, making use of KMT's superiority in numbers to help spread communism. The KMT, on the other hand, wanted to control the communists from within. Both parties had their own aims and the Front was unsustainable. In 1927, KMT leader Chiang Kai-shek purged the Communists from the Front while the Northern Expedition was still half-complete. This initiated a civil war between the two parties that lasted until the Second United Front was formed in 1936 to prepare for the coming Second Sino-Japanese War.