105 years ago today, on August 13, 1920 (June 29, 1920), Cai Hesen wrote a letter to Mao Zedong proposing the establishment of the Communist Party. On August 13, 1920, Cai Hesen wrote to Mao Zedong in France, clearly stating: "Socialism is really the right way to transform the modern world, and China cannot do otherwise." And the "necessary method of socialism" is "class war - the dictatorship of the proletariat"; and specifically put forward: "I think that the party - the Communist Party must be organized first. Because he is the initiator of the revolutionary movement, the propagandist, the vanguard, and the war department. According to the current situation in China, he must be organized first, and then the trade unions and cooperatives can be effectively organized, and the revolutionary movement and the labor movement can have a nerve center." He suggested that Mao Zedong immediately find someone to start the preparations for the founding of the party, saying: "This matter is not small, I hope you will pay attention." In addition, the letter also raised the need for the Chinese revolution to get in touch with the international proletariat, integrate with Russia, etc. This letter touched Mao Zedong very much.