Although entire Vietnam was freed in 1975 and the two parts were united a year later, many problems remained. Ha Noi wanted to conquer Laos and Cambodia, too. In 1975, the two countries were reigned by communists. In Cambodia, the Pol-Pot regime massacred those who had a different view. Many people immigrated to Vietnam, but the Chinese ethnic was pursued there. The Red-Khmers reigning over Cambodia accused Vietnam of interfering in their internal politics and attacked it in 1977. By the end of the year, the Vietnamese drove them back to 40 miles from Phnom Penh, the capital. Since Pol-Pot refused the peace proposal, the fights went on that resulted a Vietnamese invasion in 1978. Then China came that wanted to revenge on the pursuit of the Chinese in Vietnam and supported Pol-Pot. They also wanted to equalize the Soviet influence. In February 1979, the Chinese troops attacked Ha Noi, but they didn't want a long-lasting war and draw back to the border a month later.
The war in Cambodia ended in 1989 when the pressure of the economy and of the foreign countries made Vietnam withdraw from the region.