Editing Xi'an Incident (section)

=== Formation of a northwestern alliance ===
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Simultaneous to the negotiations with the Nationalist central government, the Communists also opened direct, clandestine negotiations with Nationalist army leaders. In October 1935 the Communists had arrived in [[northern Shaanxi]] at the end of the [[Long March]]. Their new base area was economically backwards, agriculturally unproductive, and cut off from the outside world.{{sfn|Qian|2024|pp=129-130}} It was bordered to the north by the [[Ordos Desert]], to the east by Shanxi (governed by the warlord [[Yan Xishan]]), and to the south and west by the 130,000-strong [[Northeastern Army]], led by [[Zhang Xueliang]], and the 40,000-strong Northwestern Army, led by [[Yang Hucheng]].{{sfn|Coble|1991|p=342}} Both Yang and Zhang were former warlords who had pledged their armies to the Nationalist Government. Zhang had governed Manchuria before it was overrun by the Japanese, and strongly wished to retake his homeland.{{sfn|Hammond|2023|p=32}} He opposed the concessions that Chiang had made to Japan, and was frustrated by his orders to fight the Communists rather than the Japanese.{{sfn|Coble|1991|pp=224-225}} Yang had likewise become skeptical of Chiang's anti-Japanese commitment after the public demonstrations in December 1935.{{sfn|Itoh|2016|p=108}} Zhang and Yang had been promised an easy victory against the Communists. They were surprised and dismayed when the Red Army defeated them in several major engagements. The Red Army treated their POWs well and gave them a political education, sending them back to spread the word that the Communists wanted to form an anti-Chiang and anti-Japanese alliance.{{sfn|Itoh|2016|pp=106–107}} This effectively destroyed morale in the Nationalist armies, and the soldiers began pressing for a truce with the Communists.{{sfn|Itoh|2016|p=107}} With his officer [[Nan Hanchen]] acting as intermediary, Yang Hucheng was able to conclude a ceasefire quickly.{{sfn|Yang|1990|p=187}} They formalized a non-aggression pact in May 1936.{{sfn|van de Ven|2003|p=179}}

Negotiations with Zhang Xueliang took longer because the CCP had no established contacts in the Northeastern Army. But after Dong Jianwu requested passage to CCP territory on a mission from the central government, Zhang realized that the central government was negotiating with the CCP and was encouraged to do so himself.{{sfn|Itoh|2016|pp=115, 124-125}} A ceasefire was agreed on February 25.{{sfn|Itoh|2016|p=118}} On April 9, Zhang Xueliang met with Zhou Enlai. Zhou, an experienced negotiator, was able to solidify the ceasefire and secure supplies for the Red Army.{{sfn|Yang|1990|p=221}} In this and subsequent meetings, Zhang Xueliang would argue that resisting Japan would only be possible if the CCP gave up its opposition to Chiang. Zhou said that the CCP would discuss the point, but refused to commit to changing the policy.{{sfn|Itoh|2016|pp=119-120,123,127}} As negotiations between Zhang and the CCP continued, the Communists infiltrated the Northeastern Army. They spread communist ideas among the soldiers and recruited officers into secret societies.{{sfn|Yang|1990|pp=221-223}} In June they set up an officer training camp that celebrated the united front.{{sfn|Coble|1991|p=342}} This support from within the army helped them to persuade Zhang to form an alliance. They concluded a formal agreement on September 22.{{sfn|van de Ven|2003|p=179}}

{{Quote box|The [CCP]'s call for suspending the civil war and forming a united anti-Japanese resistance touched not only my heart deeply but also the hearts of most of the men in the Northeastern Army.|source=Zhang Xueliang{{sfn|Itoh|2016|p=115}}|width=25%|align=right| style = padding:8px;}}

Yan Xishan also moved towards a united front with the CCP. Illegally imported Japanese products were undermining the Shanxi economy and the Japanese puppet [[Mengjiang|Mongol Military Government]] was encroaching on Yan's rule over [[Suiyuan]].{{sfn|Gillin|1967|pp=228-230}} Out of fear of the Japanese, Yan accepted Mao's overtures and agreed to a truce in June 1936.{{sfn|Gillin|1967|p=232}} In September, he created the "League for Sacrifice and Salvation" to agitate the Shanxi public against the Japanese. CCP leaders [[Bo Yibo]] and [[Feng Xuefeng]] began working closely with Yan.{{sfn|van de Ven|2003|p=180}}

The members of this northwestern alliance were united by their desire to resist Japan, but they differed over the details of how this could best be accomplished.{{sfn|van de Ven|2003|p=179}} The Communists supported a plan to use Soviet support to take over [[Shaanxi]], [[Gansu]], [[Ningxia]], [[Qinghai]], and [[Xinjiang]] and turn northwest China into a base under Zhang's command to resist Japan and oppose Chiang.{{sfn|Yang|2020|p=64}} Zhang, Yang, and Yan were still committed to convincing Chiang to lead the anti-Japanese resistance.{{sfn|van de Ven|2003|p=179}} As they continued to negotiate, they kept their alliance secret and even staged fake military battles to deceive the Nanjing government.{{sfn|Barnouin|Yu|2006|p=65}}{{sfn|van de Ven|2003|p=179}}