Operation Ranch Hand was a U.S. military operation during the Vietnam War, lasting from 1962 until 1971. It was part of the overall herbicidal warfare program during the war called "Operation Trail Dust". Ranch Hand involved spraying an estimated 20 million U.S. gallons (76,000 m3) of defoliants and herbicides over rural areas of South Vietnam in an attempt to deprive the Viet Cong of food and vegetation cover. Areas of Laos and Cambodia were also sprayed to a lesser extent. Nearly 20,000 sorties were flown between 1961 and 1971. The Vietnamese government estimates that 400,000 people were killed or maimed and 500,000 children born with birth defects as a result of this spraying of what were called by the Americans 'rainbow herbicides'.