June 1963: the PRC published The Chinese Communist Party’s Proposal Concerning the General Line of the International Communist Movement , and the USSR replied with an Open Letter of the Communist Party of the Soviet Union;  these were the final, formal communications between the two Communist parties.
- 1964: China has atomic bomb. Mao said that a counter-revolution in the USSR had re-established capitalism; consequently, the Chinese and Russian Communist parties broke relations, and the Warsaw Pact Communist parties followed Soviet suit.
- 1966-1976: Mao’s Cultural Revolution
Meant to re-establish Mao’s sole leadership of China. Aggravated, then severed PRC-USSR relations and relations with most of the Western world. Still, communist pragmatism: USSR and PRC gave aid to the Vietnamese communists led by Ho Chi Minh. The Chinese permitted Soviet aid materials to travel through China to North Vietnam during the Vietnam War (1945-1975).
- 1967: Red Guards besiege Soviet embassy in Beijing.
Despite unbroken formal diplomatic ties, relations froze in place. The PRC then raised the matter of the Sino–Soviet territorial frontier – Although demanding no territory, the Chinese insisted upon Soviet acknowledgement of that historic Russian injustice against China committed with the Treaty of Aigun (1858) and the Convention of Peking (1860); the Soviets ignored the matter.
- 1968: Border Tensions
The Soviet Army had amassed along the 4,380 km (2,738 mi.) frontier with China — especially at the Xinjiang border, in north-west China, where Turkic separatists might easily be induced to insurrection. Earlier, in 1961, the USSR had some 12 half-strength divisions and 200 aircraft at that border, seven years later, at the end of 1968, they had 25 divisions, 1,200 aircraft, and 120 medium-range missiles deployed there.
- 1969: Political border tensions turn into armed raids and small scale warfare.
Observers predicted inter-communist war. Soviet sources implied a possible first strike against China and military documents indicate that the USSR has more nuclear attack plans against China than against the US. China built large scale underground shelters.
They did not resort to full-scale war. In October, the PRC and USSR began border-demarcation talks, restoring minimal diplomatic communication.
- 1970: Mao understood that the PRC could not simultaneously confront the USSR and the USA, and suppress internal disorder. During that year, when the Vietnam War was at its worst, and Chinese anti-American rhetoric at its zenith, Mao perceived that China’s geographic neighbors, the Soviets, were the greater threat, and thus Mao sought a pragmatic rapprochement with the US, in confronting the USSR.
- 1971: Henry Kissinger visits China.
- 1972: Nixon visits China.
In the 1970s, Sino-Soviet rivalry extended to Africa and the Middle East, where each Communist power funded and supported political parties, armed movements, and states, vis-à-vis the Ogaden War (1977–78) between Ethiopia and Somalia, the Rhodesian Bush War (1964–79), the Zimbabwean Gukurahundi (1980–87), the Angolan Civil War (1975–2002), the Mozambican Civil War (1977–92), and Palestinian factions.
- 1971: Radical phase of Cultural Revolution comes to an end.
PRC gradually begins to return to Communist political normality. The re-establishment of Chinese domestic tranquility ended direct armed conflict with the USSR but did not improve diplomatic relations.
- 1973: Soviet garrisons on the border are double the size of 1969 garrisons. China continued denouncing “Soviet social imperialism” and accusing the USSR of being enemy to world revolution.
- September 1976: Mao dies.
- 1975: Vietnam War ends, Communist victory.
This left Pro-Soviet regimes in Vietnam and Laos, and a pro-Chinese regime in Cambodia.
- 1978: Pol Pot Khmer Rouge Regime in Democratic Kampuchia [Cambodia]
At first the Vietnamese ignored the Khmer Rouge’s murderous domestic policies in Cambodia, but, when their societal reorganization attacked the ethnic Vietnamese in Cambodia, Vietnam deposed Pol Pot in 1978.
- 1975-1979: Ca