Before the outbreak of the Marco Polo Bridge Incident in 1937, Chiang Kai-shek and his Nationalist government in Nanjing had nearly 2 million troops, and the Kuomintang(KMT) had basically unified China. At the same time, the Communist Party of China (CPC) only had around 20,000 party members and 30,000 Red Army soldiers, and only controlled around a dozen counties in the border region between Shaanxi and Gansu provinces. Against this background, the two Parties had reached a preliminary agreement on the reform and reorganization of the CPC’s Soviet-style government and the Red Army. However, they had not implemented a specific approach, and the strain and hostility developed during ten years of civil war had not disappeared. After the eruption of the Marco Polo Bridge Incident, the flames of war swiftly spread, and the Japanese army rapidly invaded Shanxi province, directly threatening the security of the CPC’s base in North Shaanxi province. The Red Army accelerated its reorganization and sent troops to Shanxi province, where it was forced to cooperate with the KMT army in order to defend against the Japanese. However, this was the first time the CPC and Mao Zedong had faced such a complicated, fast-changing political and military situation. They therefore endured devastating losses. This is because, before entering battle, they needed to resolve questions about the legitimacy of the Party, its military capability, its political power, and its defense, but they also needed to make every attempt to prevent the Japanese from occupying Shanxi province. They also suffered losses because they wanted to display their strength to inspire the other armies in North China, but they needed to avoid fighting the Japanese in a situation in which 20,000 to 30,000 Red Army troops were completely unfamiliar with both the situation and necessary military tactics such as dispersal. Because of these problems, the Central Committee of the CPC split over issues like deployment speeds, combat, and command leadership. However, even after the core of the Red Army went to the battlefield in late September of 1937, the area of military operations and development with which Mao Zedong and the other leaders were primarily concerned was limited to Shanxi province. Only after the Japanese occupied most of Shanxi did the policies of developing in the rear areas and building a base of operations in the plains gradually arise in discussions of the agenda among Mao Zedong and the Central Military Committee of the CPC.