The Sino-Vietnamese War was a conflict between China and Vietnam that occurred in 1979. It was primarily triggered by Vietnam's invasion of Cambodia to overthrow the Khmer Rouge, which was supported by China. The war lasted about a month, with China launching a military offensive into northern Vietnam. Despite initial Chinese advances, the conflict resulted in heavy casualties on both sides and ended with China withdrawing its troops. The war had lasting effects on Sino-Vietnamese relations and influenced regional dynamics in Southeast Asia. It highlighted the complexities of alliances and territorial disputes in the region.