city to escape the fighting between their own government troops, the NVA/NLF, the South Vietnamese and its allies, and the Khmer Rouge. By 1975, the population was 3 million, the bulk of whom were refugees from the fighting. The city fell to the Khmer Rouge on April 17, 1975. All of its residents, including those who were wealthy and educated, were evacuated from the city and forced to do labour on rural farms as "new people". TuolSleng High School was taken over by Pol Pot's forces and was turned into the S-21 prison camp, where people were detained and tortured. Pol Pot sought a return to an agrarian economy and therefore killed many people perceived as educated, "lazy", or political enemies. Many others starved to death as a result of failure of the agrarian society and the sale of Cambodia's rice to China in exchange for bullets and weaponry. The former high school is now the TuolSleng Genocide Museum, where Khmer Rouge torture devices and photos of their victims are displayed. ChoeungEk (The Killing Fields), 15 kilometres (9 mi) away, where the Khmer Rouge marched prisoners from TuolSleng to be murdered and buried in shallow pits, is also now a memorial to those who were killed by the regime.
The Khmer Rouge were driven out of Phnom Penh by the Vietnamese in 1979, and people began to return to the city. Vietnam is historically a state with which Cambodia has had many conflicts, therefore this liberation was and is viewed with mixed emotions by the Cambodians. A period of reconstruction began, spurred by the continuing stability of government, attracting new foreign investment and aid by countries including France, Australia, and Japan. Loans were made from the Asian Development Bank and the World Bank to reinstate a clean water supply, roads and other infrastructure. The 1998 Census put Phnom Penh's population at 862,000; and the 2008 census was 1.3 million
