The war with China was useless, totally avoidable, very unfortunate event, avoidable same for the war with the US and Cambodia. Honestly I don’t want to indulge the past. That brings nothing good.
Here root of the conflict. The Vietnamese resentment towards China goes back in much older days in the 1950s. During the Geneva peace negotiation where the fate of Vietnam was decided the Chinese colluded with the French, with the western power. Pham van Dong, then the government chief of North Vietnam. The Vietnamese were very angry, feeling betrayed.