At the Treaty of Geneva in 1954, Indo-China was divided into Laos, Cambodia, North Vietnam and South Vietnam, although it was agreed to hold elections in 1956 to unify the two parts of Vietnam.
Ngo Dinh Diem, the ruler of South Vietnam, refused to hold elections.
Ho Chi Minh was a communist, who was supported by China. In 1960, he set up the National Liberation Front (NLF) in South Vietnam, which started a guerrilla war to take over South Vietnam from Diem and his American backers.
The Americans called the NLF guerrillas the Vietcong, and supported Diem with military advisers and money.
Diem's government was made up of rich Christian landowners. It was corrupt and unpopular and persecuted the poor Buddhist peasants. By 1963, most of South Vietnam's rural areas were under Vietcong control - the ARVN (South Vietnamese army) could not defeat them.
In 1963, the US supported a military coup, which murdered Diem and put a military government in South Vietnam.
In August 1964, sailors on the American warship USS Maddox…