Excerpts from Books and Wikipedia
"Carpet-bombing of Cambodian territory by US forces in an attempt to cut supply routes used by the Viet Cong guerrillas against South Vietnam seriously destabilized the country in the early 1970s. This, combined with the end of US aid to the Cambodian government after the cease-fire in Vietnam in 1973, helped the communist guerrillas of the Khmer Rouge to finally take the nations capital, Phnom Penh. . . . The Khmer Rouge leader, Pol Pot, announced the arrival of Year Zero, marking a complete break with the past. . . . Cities were cleared of their inhabitants. They found themselves enslaved and starving in gigantic collective farms. Money, education, private property, and religion were forbidden. In its short life, Poll Pot's regime murdered between one and three million of its own people." [Furtado: 1001 Days]