"the Vietcong and the Americans"
The Vietnam War started in 1955 and lasted for twenty years, resulting in the deaths of over six million people.  The Viet Cong and the North Vietnamese Army were Communist; they fought the Southern Vietnamese who became allied with the Americans.  The USA’s reason for entering the war were complex, but can be generally understood to be part of their policy of Containment (as instigated in the Truman Doctrine of 1947); a key element of the Cold War, this meant a wish to halt the spread of Communism.  The war was the first involving the USA in which the media played a huge part in public perception of the ongoing events, with graphic images and reports being shown nightly on the television news.  It also sparked an enormous protest movement, as so many people became opposed to the US intervention and loss of life.  The US involvement ended in April 1975, when all personnel were evacuated from the falling city of Saigon by helicopter leaving many desperate Vietnamese allies to await their fate at the hands of the approaching Viet Cong and NVA.  The US troops returning home – many of whom were extremely young and had been drafted – did not receive the warm welcome that the previous generation of soldiers had experienced at the end of WW2.  There was a perception that they were to blame for the loss of the war, and they also received criticism from the peace movement.  Many veterans still suffer from PTSD as a result of inadequate support upon their homecoming.   

'Platoon' is one of many powerful films to have been made about the conflict.