In response to the Vietnamese invasion of Cambodia, China launches an invasion of Vietnam. Tensions between Vietnam and China increased dramatically after the end of the Vietnam War in 1975. Attempting to expand its influence in Indochina, Vietnam established a military presence in Laos; strengthened its ties with China's rival, the Soviet Union; and toppled the Cambodian regime of Pol Pot in 1979. Just over a month later, Chinese forces invaded, but were repulsed in nine days of bloody and bitter fighting. Tensions between China and Vietnam remained high throughout the next decade, and much of Vietnam's scarce resources were allocated to protecting its border with China and its interests in Cambodia.