中ソ国境紛争
In October 1969, after the seven-month Sino-Soviet border conflict, in Beijing, Premier Alexei Kosygin secretly spoke with Premier Zhou Enlai to determine jointly the demarcation of the Sino-Soviet border. Despite the border demarcation remaining indeterminate, the premiers' meetings restored Sino-Soviet diplomatic communications, which by 1970 allowed Mao to understand that the PRC could not simultaneously fight the US and the USSR while suppressing internal disorders throughout China. In July 1971, the US advisor for national security, Henry Kissinger, went to Beijing to arrange for President Nixon's visit to China. Kissinger's Sino-American rapprochement offended the USSR, and Brezhnev then convoked a summit-meeting with Nixon, which re-cast the bi-polar geopolitics of the US-Soviet cold war into the tri-polar geopolitics of the PRC-US-USSR cold war.