A Tract of Time is an antiwar novel from 1966 by Smith Hempstone, that covers the time period about 1960, when there was an attempted coup of South Vietnamese President Ngo Dinh Diem. Even as the United States backed Diem's government during the war, its American advisers worked with the Montagnard people who opposed Diem, to help them fight the Viet Cong, whom they also opposed. The book follows one CIA operative, Harry Coltart, as he works with the Montagnard mountain tribesmen in the Central Highlands. Harry is initially successful in getting the Montagnards to fight against the Viet Cong, but then the Montagnards are betrayed and South Vietnamese troops are sent in. Harry has to be rescued as the Montagnards join the Viet Cong.