1. 20世纪70年代中后期，中越边境陷入领土纠纷的危机并最终导致中国发动对越自卫反击战，中越两国友好关系因此破裂。
During the middle and later of the 1970s, China and Vietnam was trapped into the territorial disputes in the border of Sino-Vietnam and then caused the counterattack in self-defense on China-Vietnam border finally.