How did tensions along the Sino-Soviet border influence the later Cultural Revolution?

Tensions along the Sino-Soviet border significantly influenced the trajectory of the Cultural Revolution, particularly by acting as a catalyst for ending its most radical phase.12

While Mao Zedong initially launched the Cultural Revolution to purge "revisionist" elements he believed mirrored the Soviet Union's own political degeneration, the escalation of external threats eventually forced a shift in priorities. By 1968, the Soviet invasion of Czechoslovakia and the subsequent articulation of the Brezhnev Doctrine—which justified Soviet intervention in socialist states—greatly heightened China’s sense of insecurity.132

This fear was compounded by the Soviet military buildup along the Sino-Soviet border since 1966. Faced with the potential for a Soviet invasion while the country remained paralyzed by internal chaos and factional violence, Mao moved to restore order. The military, which had been tasked with bringing stability to urban centers, solidified its control over the state and party apparatus. By the time the Ninth Party Congress convened in 1969, following bloody border clashes, the government was dominated by military figures, and the focus of Chinese politics shifted toward national security and conventional diplomacy, including efforts to resume talks with the United States.21