Sino-Soviet split

From the late 1950s the alliance between the People's Republic of China and the Soviet Union, the two great communist powers, fell apart in what became known as the Sino-Soviet split. What began as a quarrel over Marxist–Leninist doctrine and Soviet foreign policy grew into open rivalry, armed clashes on the border in 1969 and a realignment that drew China towards the United States. It turned the Cold War from a contest between two blocs into a three-sided one, and lasted until relations were normalised in 1989.

After the Communists won the Chinese civil war in 1949, Mao Zedong and Joseph Stalin signed a Treaty of Friendship, Alliance and Mutual Assistance in 1950. Moscow lent China $300 million, promised military help against Japan and handed back railway and port rights in Manchuria, while China recognised the independence of Mongolia. Nikita Khrushchev improved the terms in 1954 with trade deals, industrial projects and thousands of Soviet technicians and advisers. By 1955 most of China's exports went to the Soviet Union. Yet Mao and Khrushchev disliked one another, personally and politically.

In 1956 Khrushchev denounced Stalin and his cult of personality and began de-Stalinisation. Mao and the Chinese leadership were dismayed, and came to see Soviet talk of peaceful coexistence with the West as revisionism, a betrayal of revolutionary principles. Moscow, for its part, feared that Mao was careless about the dangers of nuclear war, and in 1959 Khrushchev publicly criticised the people's communes of the Great Leap Forward, deeply offending Mao. At a Romanian party congress in June 1960 the two sides traded insults in public, and that summer Khrushchev withdrew about 1,400 Soviet technicians from China (Chinese records give 1,390), cancelling some 200 joint scientific projects. In 1961 the Soviet Union broke off relations with Albania, China's ally in Europe, and the dispute moved from party to state level. In 1962 Mao mocked Khrushchev's retreat in the Cuban Missile Crisis, and Beijing resented Moscow's growing ties with India, its rival in a border dispute.

During the Cultural Revolution, which began in 1966, China denounced the Soviet Union as a "social imperialist" power, especially after the Soviet invasion of Czechoslovakia in 1968. Beijing also asked Moscow to admit that the 19th-century treaties fixing their border had been unjust, a request the Soviets ignored. By 1968 large Soviet forces, including 16 divisions, 1,200 aircraft and 120 medium-range missiles, faced China along a frontier of some 4,380 kilometres. In March 1969 fighting broke out at Zhenbao Island on the Ussuri River and at other points. The Soviet Union reportedly considered a large-scale nuclear strike on China, and Chinese leaders left Beijing for safety before the two sides resumed talks.

The rivalry encouraged Mao to seek an understanding with the United States, symbolised by Richard Nixon's presidential visit to China in 1972. Both communist powers kept supplying North Vietnam, but they competed for influence elsewhere. After Mao's death in 1976, Deng Xiaoping pursued a pragmatic course: China established diplomatic relations with the United States on 1 January 1979 and attacked Soviet-backed Vietnam that year. When the Soviet Union invaded Afghanistan in December 1979, China suspended talks on normalisation, let the old alliance treaty lapse and helped arm the Afghan resistance.

In March 1982 Leonid Brezhnev called for better relations in a speech at Tashkent, and negotiations resumed that autumn. Deng named three obstacles: Soviet support for Vietnam's occupation of Cambodia, the Soviet military build-up on China's borders, and the occupation of Afghanistan. Relations were finally normalised when Mikhail Gorbachev visited Beijing in 1989, shortly before the Tiananmen Square crackdown that June.

Our 1960 and 1985 maps show the Soviet Union and China sharing their long frontier, first as allies and then as rivals.