In February 1979, Chinese leadership, with the armed forces of 600,000, invaded Vietnam, with a record of many brutal war crimes. Why? It also turned out that the Pol Pot faction, under the direction of Chinese military 'advisors,' had committed one of the most terrible genocidal crimes, murdering about three million people. Why? On the other hand, we have seen few record of despotic suppression in Vietnam, in spite of the fact that there have been many difficult economic conditions as well as the awful scars left by the war crimes committed by U.S. and Chinese aggressors. Why? The author tries to explain the social basis of such phenomena as Chinese big-power hegemonism, the genocidal despotism in Pol Pot Cambodia as well as the democratic character of the Vietnam revolution. He also tries to analyze the big-power hegemonism of the Soviet leadership and the contradictions in the international relations. In conclusion, he gives the perspectives on the developments in the COMECON countries, the Third World and the advanced imperialist countries, and warns the public of the danger of nuclear extinction.