From 1968-1974, the United States bombed Vietnamese and Khmer Rouge targets in Cambodia. Hundreds of thousands of civilians were killed in the air raids, garnering support for the Khmer Rouge among Cambodians, and in April of 1975, they overthrew the American-backed government of Lon Nol. The Khmer Rouge immediately implemented a ruthless vision for Cambodia. Cities were completely evacuated, families were separated, and 3 million people were driven into forced labor camps. Schools, hospitals, banks, and factories were shut down, and temples destroyed. Religious and professional people in any field were killed along with their extended families. People who weren't murdered faced death by starvation or exhaustion in the labor camps, or imprisonment, torture and certain death in Tuol Sleng, the notorious political prison in Phnom Penh. Until Vietnamese forces overthrew the Khmer Rouge in 1979, at least 1.7 million people died of execution, disease, starvation, torture and hard labor.