China provided material and technical support to the Vietnamese communists worth hundreds of millions of dollars. Chinese-supplied rice allowed North Vietnam to pull military-age men from the paddies and imposed a universal draft beginning in 1960. In the summer of 1962,
Mao Zedong agreed to supply Hanoi with 90,000 rifles and guns free of charge. Starting in 1965, China sent anti-aircraft units and engineering battalions to North Vietnam to repair the damage caused by American bombing, rebuild roads and railroads, and to perform other engineering works. This freed North Vietnamese army units for combat in the South. Between 1965 and 1970, over 320,000 Chinese soldiers served in North Vietnam. The peak was in 1967, when 170,000 were stationed there.