High Quality Content by WIKIPEDIA articles! The Sino?Soviet split was the gradual worsening of relations between the People's Republic of China (PRC) and the Union of Soviet Socialist Republics (USSR) during the Cold War (1945?91). Since 1956, the countries had (secretly) been diverging ideologically, and, beginning in 1961, the Chinese Communists formally denounced ?The Revisionist Traitor Group of Soviet Leadership." In the 1960s, this intellectual divergence became critical, continuing until the late 1980s ? yet was rendered moot with the USSR?s disestablishment in 1991. Their doctrinal divergence owed as much to Chinese and Russian national interest, as with the régimes? interpretative Marxist ideologies.