The Xi'an Incident.

Marshal Zhang Xueliang, Commander of the North Eastern Army, grows progressively disillusioned by Kuomintang leader Chiang Kai-shek's policy to engage the Chinese Communist Party rather than fight the Japanese invaders which are occupying Manchuria. Despite numerous pleas, Chiang does not budge. After discussing with fellow general Yang Hucheng, the two take events into their own hands and place Chiang Kai-shek under arrest on December 12, 1936, forcing Chiang into a coalition with the CCP.