In July and August 1935, the Comintern convened its seventh congress in Moscow, which focused on the question of the establishment of an anti-fascist united front.

On August 15, 1936, the Comintern sent a telegram to the Central Committee of the Communist Party of China, pointing out that the Central Committee of the Communist Party of China "is wrong to put Chiang Kai-shek and the Japanese aggressors on an equal footing", "cannot oppose both the Japanese aggressors and the struggle against Chiang Kai-shek at the same time", and "we (the International) feel that your (the CCP's) statement calling for the anti-Chiang action of the Southwest Group is wrong", and demanded that the Chinese Communists and Chiang Kai-shek hold peace talks on joint resistance against Japan.

On December 17, 1935, the Wayaobao Conference of the Communist Party of China established the policy of the anti-Japanese national united front.

In January 1936, Mao **, Zhou Enlai, Peng Dehuai and others jointly issued the "Letter to All Officers and Men of the Northeast Army for the Red Army to Cooperate with the Northeast Army to Resist Japan".

In February 1936, the CCP announced the start of the Eastern Crusade against Japan.

On April 9, 1936, Zhang Xueliang flew to Yan'an to meet Zhou Enlai.

On June 1, 1936, Chen Jitang and Li Zongren sent a telegram in Guangzhou. denounced the trampling of Chinese land by the Japanese army after the September 18 Incident, and decided to lead his troops north to resist Japan and recover the lost territory. However, soon after, the Guangdong generals surrendered to Nanjing, Chen Jitang fell, and Li Zongren had to submit to Chiang Kai-shek. Due to the peaceful settlement of the Liangguang Incident, Chiang Kai-shek transferred all the Central Divisions that were preparing to conquer Liangguang to the north to suppress the Communists, and prepared to transfer Zhang Xueliang's troops away. However, due to Chiang Kai-shek's overconfidence, only a few civilians and soldiers flew to Xi'an, and as a result, everyone was detained during the Xi'an Incident. On September 20, 1935, Chiang Kai-shek set up the Northwest Bandit Suppression General Headquarters in Xi'an, and transferred the Northeast Army to Shaanxi, Gansu and Gansu.

On August 15, 1936, the Comintern sent a telegram to the CCP, demanding that the CCP and Chiang Kai-shek hold peace talks on joint resistance against Japan.

In September 1936, the Communist Party of China and the Northeast Army formally signed the Agreement to Resist Japan and Rescue the Country.

On December 4, 1936, Chiang Kai-shek arrived in Xi'an, and on December 9, Chiang Kai-shek wrote a letter to Shao Lizi, chairman of Shaanxi Province, secretly instructing Ta Kung Pao to publish the news that Zhang Xueliang and Yang Hucheng were deprived of the right to "suppress the Communists" and replaced by Jiang Dingwen.

On October 22, 1936, Chiang Kai-shek flew from Nanjing to Xi'an and strictly ordered the Red Army to be suppressed. Zhang Xueliang objected to it in person, and put forward a request to stop the civil war and unanimously resist Japan, but Chiang refused, and the two quarreled.

On October 29, 1936, Zhang Xueliang flew to Luoyang to celebrate Chiang Kai-shek's birthday and persuaded Chiang Kai-shek to join forces to resist Japan, but Chiang refused. Chiang Kai-shek resolutely rejected his idea of going north to resist the Japanese, and forced him to suppress the Communists, otherwise he would withdraw his troops to the east.

On November 27, 1936, Zhang Xueliang wrote to Chiang Kai-shek, asking for a war of resistance, but Chiang refused.

On December 2, 1936, Zhang Xueliang flew to Luoyang to meet Jiang and demanded the release of the "Seven Gentlemen" of the Anti-Japanese Salvation Association. He reported to Chiang Kai-shek, saying that his subordinates were unstable and difficult to support, and repeatedly asked Chairman Chiang to give a lecture, and Chiang agreed to go to Xi'an and stay in Qingchi, China.

On December 7, 1936, Zhang Xueliang went to Huaqingchi to meet Chiang Kai-shek, and repeatedly asked to stop the civil war and unanimously resist Japan, but Chiang refused.

On December 10, 1936, Zhang Xueliang took Bai Fengxiang to meet Chiang Kai-shek, who was holding a meeting to formally approve the launch of the sixth "encirclement and suppression" plan, and decided to announce the mobilization order on December 12, 1936.

On the evening of December 11, 1936, Chiang Kai-shek invited Zhang Xueliang, Yang Hucheng, Jiang Dingwen, Chen Cheng, Zhu Shaoliang and others to attend a dinner. The Central Army was ordered to take over the task of suppressing the Communists from the Northeast Army and the Northwest Army

On the evening of December 11, 1936, Zhang Xueliang and Yang Hucheng respectively summoned senior generals of the Northeast Army and the 17th Route Army and announced that they would conduct military admonitions in the early morning of December 12.