In April 1975, the Cambodian capital of Phnom Penh was bombed by the Khmer Rouge. Surviving Gambodians sifted through the collapsed rubble and corpses in despair.

　　In April 1975, the Cambodian capital of Phnom Penh was bombed by the Khmer Rouge. The surviving Gambodians sifted through the crumbling rubble and corpses in despair, and on April 17, the Khmer Rouge triumphantly entered the capital, Phnom Penh. Within hours, they had transformed and disintegrated Cambodia into a rural society in service to the state. They ordered the forced evacuation of approximately 2 million residents to the countryside. Resident foreigners were deported to the Thai border, losing witnesses to the genocide in Democratic Kampuchea; between 500,000 and 1.5 million of the victims between 1975 and 1979 died from forced labor and starvation caused by the Khmer Rouge.

　　When Nixon became president of the United States in January 1968, he pledged an honorable end to the war in Vietnam. Troops and supplies from North Vietnam were pouring into South Vietnam via Cambodia. To counter the North Vietnamese forces, Nixon dramatically expanded the Cambodian bombing campaign begun by his predecessor, President Lyndon Johnson In March 1969, Nixon secretly ordered the U.S. Air Force to conduct a massive bombing campaign in eastern Cambodia to cut off North Vietnamese supply routes In April 1970, U.S. and South Vietnamese ground forces invaded eastern Cambodia and attacked communist sanctuaries. Meanwhile, North Vietnamese forces penetrated deeper into Cambodia and began occupying large parts of the countryside for the Khmer Rouge. Nixon then launched a ground invasion of Cambodia to cut off supply routes for the North Vietnamese army.

　　Although Cambodia was not a party to the Vietnam War, it was estimated that the U.S. bombing of Cambodia exceeded the total tonnage of all bombs dropped by the United States during World War II. American bombers dropped more than 2.7 million tons of bombs on more than 113,000 sites in Cambodia, inflicting heavy casualties on combatants and civilians. Tens of thousands of Cambodians were killed in the bombing campaign against Cambodia, and millions were made refugees. The destruction caused by the mass bombings and the partial occupation by the U.S. military in 1970 prompted the rise of the communist Khmer Rouge regime, which subsequently enforced genocide, and the Khmer Rouge regime was estimated to have massacred some 2 million Cambodians.