Since the People's Republic of China (PRC) formed an official literature and art policy, there have often been rectification campaigns in mainland China's literary and art circles. Mao Zedong did not form his own views on literature and art, though he himself occasionally wrote poems. He inherited the "Party spirit" ideology of proletarian literature and art, advocated by Marx and Engels and further developed lby Lenin and Stalin. During the Yan'an Period, he decided to follow Stalin in demanding that literature and art serve the workers, peasants and soldiers as these groups, along with the urban petty bourgeoisie, constituted more than 90 percent of the total population of China. He reiterated Lenin's remark that literature and art were "cogs and screws" destined to fulfill their allotted roles in the "proletarian machine," and should not be allowed to develop freely. Although Mao has been dead for more than two decades, his ideas on literature and art still remain dominant in mainland China. In literature and art policy, Mao did copy both from Lenin and Stalin, leading to the Sovietization of literature and art in mainland China. The Cultural Revolution marked the climax of this Sovietization tragedy.