The Sino-Soviet split (1960–1989) was the deterioration of political and ideological relations between the neighboring states of People's Republic of China (PRC) and the Union of Soviet Socialist Republics (USSR) during the Cold War. In the 1960s, China and the Soviet Union were the two largest communist states in the world. The doctrinal divergence derived from Chinese and Russian national interests, and from the régimes' different interpretations of Marxism–Leninism.