Answer:
Vietnam launched an invasion of Cambodia in late December 1978 to remove Pol Pot. Two million Cambodians had died at the hands of his Khmer Rouge regime and Pol Pot's troops had conducted bloody cross-border raids into Vietnam, Cambodia's historic enemy, massacring civilians and torching villages.
Explanation: Here you go! I searched this up btw it was on a website called bbc.com. I hope this helped and have a wonderful day!