The war fought in Vietnam from 1955 to 1975, involving significant U.S. military presence, is known as the Vietnam War. It was a complex conflict rooted in the struggle between communist North Vietnam and non-communist South Vietnam, with the U.S. intervening to prevent the spread of communism in Southeast Asia. The war was marked by intense guerrilla warfare, significant civilian casualties, and controversial tactics like aerial bombings. The eventual fall of Saigon in 1975 led to the reunification of Vietnam under communist control, leaving profound impacts on U.S. foreign policy and society.