Three momentous events of the 1960's—the war in Vietnam, the steady worsening of the Sino-Soviet dispute, and the Chinese acquisition of nuclear weapons—portend a shift in the political center of gravity from Europe to Asia in the last third of this century. The Soviet invasion of Czechoslovakia only temporarily ruffled Europe's political terrain, and, while it damaged Moscow's international prestige, it never threatened to'escalate into superpower confrontation on the continent. The United States and its North Adantic Treaty Organization (NATO) allies, in fact, went out of their way to avoid provoking the Soviet Union; the ritualistic tone of their denunciations of the invasion indicated that, as after Hungary in 1956, the West was resigned to Moscow's freedom of action in its Eastern European “sphere of influence”. Emboldened by the Western response, the Soviet Union reiterated with increased vigor its proposal for a European security conference to freeze the status quo in Europe.