Which nation invaded Cambodia in 1979, leading to the fall of the Khmer Rouge?

• A. China
• B. Japan
• C. United States
• D. Vietnam

Answer: (D)

Regional intervention in Southeast Asia during the late 1970s is what this item focuses on. In late 1978 into 1979, Vietnam launched a full-scale invasion of Cambodia to topple the Khmer Rouge regime, which had seized power in 1975 and was responsible for brutal purges and genocidal policies. Vietnam also cited cross-border attacks by Khmer Rouge forces into Vietnam as a security threat. The invasion quickly led to the fall of Phnom Penh and the collapse of Khmer Rouge rule.

After the offensive, Vietnam installed a new government in Cambodia—the People’s Republic of Kampuchea—that aligned with Hanoi and the Soviet bloc. The Khmer Rouge retreated to border areas and continued a guerrilla war from camps along the Thai border, receiving some outside support, primarily from China, while the United States and others did not conduct a direct invasion themselves.

So the nation that invaded and helped end the Khmer Rouge regime was Vietnam.