China and the Viet Minh had a history of working with each other even before the war: Chinese communists and the Viet Minh provided each other with cover and material support during their struggles to gain control in their own countries.

The Gulf of Tonkin incident in 1964 with the arrival of U.S. combat troops triggered an escalation in Chinese support. Beijing sent thousands of engineering troops into North Vietnam to help repair roads, railways, airstrips and critical defence infrastructure. Between 1965 and 1971, more than 320,000 Chinese troops were deployed in North Vietnam.

The relationship between North Vietnam and China deteriorated in the 1960s. Changes in leadership in Moscow and the Cultural Revolution in China in 1966 increased the tension between the two communist superpowers. In November 1968, the Soviet Union and North Vietnam signed a new set of military and economic agreements, meaning that the North Vietnam made its decision of choosing Moscow over Beijing. Responding to that, Chairman Mao winded back Chinese aid and then all Chinese personnel withdrew from North Vietnam.