After the September 18 Incident, hundreds of thousands of soldiers of the Northeast Army were forced to withdraw into Guannei due to the implementation of Chiang Kai-shek's order not to resist. Because of the loss of the land on which it depended for its survival, it meant that all the future military expenses and supplies of the Northeast Army would need to rely on Nanjing for supply. The predecessor of the Northeast Army was the army of the Fengzhi warlords, not Chiang Kai-shek's concubines, and naturally the Nationalist government could not have raised such a huge army in vain.
So the Northeast Army was transferred to the northwest to encircle and suppress the Red Army, which had just reached northern Shaanxi, and after several encounters, the Northeast Army suffered heavy losses, which not only did not receive Chiang Kai-shek's sympathy, but also took the opportunity to order the abolition of several units annihilated by the Red Army. Bearing the insult of not resisting the general, and at the same time being suppressed and exploited by the Nationalist government in Nanjing, which completely angered Zhang Xueliang's dissatisfaction, so on December 12, 1936, Zhang Xueliang and Yang Hucheng, the general of the Northwest Army, carried out "military advice" against Chiang Kai-shek, demanding that the civil war stop and unite to resist Japan.
This historical event is known as the Xi'an Incident, or the Double Twelve Incident, of course, the incident was properly resolved in the end, and the second cooperation between the Kuomintang and the Communist Party was ushered in, and the anti-Japanese national united front gradually took shape. Many people may have such a question, if Chiang Kai-shek was killed by the Northeast Army or the Northwest Army after the Xi'an Incident, how would China's War of Resistance Against Japan develop after the Japanese army launched a full-scale war of aggression against China on July 7, 1937?
If Chiang Kai-shek had been denounced during the Xi'an Incident, the biggest beneficiary would have been the Japanese army, and the warlord division situation that had just ended in the country might have resurrected, and it was very likely that a united front would not have taken shape. In addition, a major war between the Central Army and the Northeast Army and the Northwest Army will be inevitable, and at this time, the Japanese army that is eager to move will seize the opportunity to invade the south of Guannan on a large scale, because the domestic armies are fighting separately and scattered, the Japanese army is likely to end the war within a year.