China invades Vietnam

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, 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.