Complex sentence: Over the course of the next twenty years, that emphasis on cultural transformation would be adopted by virtually all elements of the radical Chinese left; and its rhetoric--if not its substance--would eventually be used by Mao to justify the Cultural Revolution.
Split into simpler sentences: Over the course of the next twenty years, that emphasis on cultural transformation would be adopted by virtually all elements of the radical Chinese left. Its rhetoric, if not its substance, would eventually be used by Mao to justify the Cultural Revolution.