A CPC manifesto and a statement by Chiang Kai-shek signified that the Chinese united front against Japanese aggression was formally taking shape.

While the main force of the Japanese Army was engaged in a strategic offensive in northern China, on August 13, in central China, another Japanese force began to attack Shanghai in an incident that sent shockwaves rippling across the whole country. Following this attack, which posed a direct threat to the National Government's capital of Nanjing, Chiang Kai-shek made a fundamental shift in his policy on resistance against Japanese aggression. On August 14, the National Government issued a statement on engaging in self-defense, announcing that China had been pushed over the edge by Japan's endless acts of aggression, and that the country was left with no choice but to defend itself and stand up to this violence.

With this new development, on August 18, the KMT and the CPC reached an agreement on the reorganization of the Red Army and personnel issues in the Shaanxi-Gansu-Ningxia Border Region. On September 22, the KMT published the Manifesto of the CPC Central Committee on the Establishment of KMT-CPC Cooperation via the Central News Agency. The next day, Chiang Kai-shek made a statement announcing that, "the manifesto issued by the CPC shows that national consciousness tops all else," which was essentially a nod to the CPC's legitimacy throughout the country. The CPC manifesto and Chiang Kai-shek's statement indicated that the Chinese united front against Japanese aggression rooted in KMT-CPC cooperation was formally taking shape. This came as a result of the CPC's decisions in response to a changing context and the shift in KMT policy.

(Source: The Chinese War of Resistance Against Japanese Aggression: A Concise History)