 Complete the following phrase:  In January 1923, Qu accepted the invitation from Chen Duxiu, leader of the Chinese Communist Party at that time, to come back from Russia to join in his cause. After returning, Qu was responsible for the propaganda work of Communist Party of China. In 1927 after the fall of Chen Duxiu, he became acting Chairman of the CCP Politburo and the de facto leader of the party. He organised actions such as the 