Romanian Communist Party congress, when Khrushchev and Peng Zhen openly quarreled. Premier Khrushchev insulted Chairman Mao Zedong as “a nationalist, an adventurist, and a deviationist”. In turn, Mao insulted Khrushchev as a Marxist revisionist, criticizing him as “patriarchal, arbitrary and tyrannical”. In follow-up, Khrushchev denounced China with an eighty-page letter to the conference.
Khrushchev also withdrew nearly all Soviet technical experts from China, leaving some major projects in an unfinished state. Many blueprints and specifications were also withdrawn.
November 1960, at a congress of 81 Communist parties in Moscow, the Chinese quarreled with the Russians and with most other Communist party delegations — yet compromised to avoid a formal ideological splitting; nonetheless, in October 1961, at the 22nd Congress of the Communist Party of the Soviet Union they again quarreled openly. In December, the USSR severed diplomatic relations with the People’s Socialist Republic of Albania, graduating the Russo–Chinese ideological dispute from between political parties to between nation-states.
- 1962: Sino Indian War
USSR does not support China. Maintains moderate relation with India, greatly offending Mao Zedong.
The PRC and the USSR broke relations because of their international actions. Mao criticized Khrushchev for withdrawing from fighting the US in the Cuban Missile Crisis (1962). “Khrushchev has moved from adventurism to capitulationism”; Khrushchev replied that Mao’s confrontational policies would provoke a nuclear war.
USSR is alarmed by the Great Leap Forward. USSR has refused to aid Chinese nuclear weapons development and refused to side with them in the Sino Indian War. Mao was offended by all these actions. He perceived Khrushchev as too-conciliatory with the West, despite Soviet prudence in international politics that threatened nuclear warfare (i.e. the US and USSR were nuclear powers by the late 1950s), wherein the USSR managed superpower confrontations such as the status of post-war Berlin.
- 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 th