The Vietnam War, officially the Second Indochina Conflict, was initiated by the United States, in response to a poll conducted that suggested given the planned democratic election after the reduction of the demilitarized zone upheld until 1956 since the war would lead to a certain communist victory.
America, knowing that South Vietnam would democratically become a communist state, abstained from signing the Geneva conference of 1954 allowing this election to happen even though these were the grounds they had stated at the end of the Second World War. Since the end of the Second World War the changing political landscape had brought Communism as the new enemy of the west and its containment was considered a top priority in the United States. South Vietnam refused to have open elections and the United States supported them claiming that free elections could never be possible in the Communist control north.
A frustrated Ho Chi Minh eventually decided to militarily move into South Vietnam with his Viet Minh (later Viet Cong) as the increasingly unpopular US controlled government employed stronger tactics to maintain the South Vietnamese people under Diem. In retaliation the US sent 'advisers' to help Diem keep the situation under control before stepping up to a full scale ground war. The war was the longest in American history, lasting approximately 16 years. It was also the first war fought by America in which the stated military goals of the Americans were not met and it is now widely agreed that it is the first war America actually lost failing to win the hearts and minds of both the Vietnamese and the people back home. America left the war in 1973 under an arrangment that was supposed to keep South Vietnam free from the Communist north, but in 1975 the north invaded and quickly conquered the country. Today a United Vietnam is Communist.
Opposition to the Vietnam War
The Vietnam War is remembered as creating massive opposition in the United States. Much of the hippie movement was based in opposition to the Vietnam War and a belief in pacifism more broadly. This opposition inspired such songs as "The I Feel Like I'm Fixing to Die Rag," by Country Joe McDonald, "Give Peace a Chance," by John Lennon, "Run Through the Jungle," by Creedence Clearwater Revival, and "War," by Edwin Starr. This opposition also manifested itself in the form of protests. One of the most famous protests of this era occurred at Kent State University in Ohio, during which four students were shot and killed by the Ohio State National Guard following several days of rioting and the firebombing of the ROTC building. The shooting was later determined to be justified when a federal court dismissed the case against the eight guardsmen indicted.
It wasn't until the Reagan era that popular culture, and society, began to embrace Vietnam veterans as heroes by creating characters like John Rambo and John "Hannibal" Smith.
- Larry Berman, Perfect Spy: The Incredible Double Life of Pham Xuan An, Time Magazine (Smithsonian Books/HarperCollins, 2007). 
- SIGINT and the Fall of Saigon, April 1975.