The Sino-Soviet border conflict was a seven-month undeclared military conflict between the Soviet Union and China at the height of the Sino-Soviet split in 1969. The Soviet Union launched an invasion of China in March 1969, annexing the disputed areas in the Argun and Amur rivers. Although military clashes ceased that year (with China relinquishing territory), the underlying issues were not resolved until the 1991 Sino-Soviet Border Agreement.
The most serious of these border clashes, which brought the world's two largest communist states to the brink of war, occurred in March 1969 in the vicinity of Zhenbao (Damansky) Island on the Ussuri (Wusuli) River, where 772 People's Liberation Army soldiers and 130 Soviet Army soldiers were killed. Chinese historians usually refer to the conflict as the Zhenbao Island Incident