 With the PRC no longer espousing the anti-revisionist notion of the antagonistic contradiction between classes, relations between the two countries became gradually normalized.In 1979, however, the PRC invaded Vietnam (which had, after a period of ambivalence, sided with the Soviet Union) in response to the Vietnamese invasion of Cambodia which overthrew the China-backed Khmer Rouge from power.During the Sino-Soviet split, strained relations between China and the Soviet Union resulted in strained relations between China and the pro-Soviet Afghan communist regime.