The U.S. was quick to use worsening relations between the Soviets and China to its advantage. This event, known as the Sino-Soviet Split, led directly to the rapprochement of Chinese and American relations in the 1970’s.
China and the Soviet Union began to have a falling out as early as the 1930’s when the Soviet Union backed Chang Kai Shek rather than Mao Zedong during the Chinese Civil War. Although they appeared to become allies after World War II, the rifts began to show as ideological difference formed between the two communist countries. China wanted to continue aggressive action towards the west, which the Soviets wanted to try and pursue peace. Soon, border clashes between the two sides began to occur as well as full-blown criticism published in the international press.
Nuclear war was barely averted in 1968, but this event caused China to rethink its geopolitical strategy. They began to tone down their anti-U.S. rhetoric and sought to lessen tensions between themselves and other western superpowers. Seeing their Soviet neighbors as the greater threat, the Chinese extended diplomatic invitations to the U.S. in 1972 and reopened trade relations and international cooperation by hosting president Nixon.
The U.S. were more than happy to help drive a wedge between the two communist superpowers, which they viewed as allies until the border clashes. Soon, the Soviets and China were backing different political parties in a number of civil wars in African and the Middle East while the U.S. gleefully played them off each other while the Vietnam conflict wound down.
The main way in which the US used this was by opening relations with China in the early 1970s. The US used this lessening of tensions with China to put pressure on the Soviet Union and to extricate itself from the Vietnam War.
By 1969, relations between China and the USSR were very bad. The Chinese were concerned about the Soviet tendency to meddle in the affairs of communist countries. This helped push them towards a more friendly relationship with the US.
This helped the US in a number of ways. First, it helped the US to get out of the Vietnam War because it reduced the amount of help that China was giving North Vietnam. Second, it pressured the Soviet Union to improve relations with the US so that the US and China would not create an alliance aimed against the USSR. In this way, the US used the tensions between China and the USSR to get out of Vietnam and move towards detente.