What were the strengths and weaknesses of the communist world by the 1970s?

By the 70s, communism had reached the greatest extent of expansion. The Soviet Union had matched its military might with the U.S. However, divisions within the communist world increased, especially between Eastern Europe and the Soviet Union, China and the Soviet Union, and China and Vietnam. The horrors of Stalin's Terror and the gulag, of Mao's Cultural Revolution, and of something approaching genocide in communist Cambodia all wore away at communist claims to moral superiority over capitalism.