Excerpts from Books and Wikipedia
"The Sino-Soviet split was the breaking of political relations between the People's Republic of China (PRC) and the Union of Soviet Socialist Republics (USSR), caused by doctrinal divergences that arose from their different interpretations and practical applications of Marxism–Leninism, as influenced by their respective geopolitics during the Cold War (1945–1991). In the late 1950s and early 1960s, Sino-Soviet debates about the interpretation of orthodox Marxism became specific disputes about the USSR's policies of national de-Stalinization and international peaceful coexistence with the Western world, which CPC chairman Mao Zedong decried as revisionism. Against that ideological background, China took a belligerent stance towards the West, and publicly rejected the USSR's policy of peaceful coexistence between the Eastern and Western blocs. In addition, Beijing resented the closer Soviet ties with India, and Moscow feared Mao was too nonchalant about the horrors of nuclear war." [Wikipedia]