The Viet Cong was a communist movement dedicated to the union of North and South and had been fighting a guerrilla war against South Vietnam since 1954.
They were reinforced by North Vietnamese troops in 1959 in an effort to overthrow the South Vietnamese Government.
In 1961 the US began sending troops to the region to bring a halt to what it saw as the spread of communism in South-East Asia.
In 1965 the US started air raids on the North.
Peace talks in 1969 saw American involvement decrease but war took hold once more in 1970 when the US and South Vietnam invaded Cambodia.
A major communist offensive in 1972, coupled with strong opposition at home to US involvement in the war, led to further peace talks and the Paris Agreement in January, 1973 and the withdrawal of US troops.
Saigon fell to communist forces on 30 April 1975.
Some 900,000 Viet Cong and North Vietnamese, 50 000 Americans, and about 400,000 South Vietnamese had died.