I ordered this complete mini-series for video a couple weeks ago. It starts with the mostly unknown first ("French") Vietnam war. The French lose the war. The Vietnamese gain independence, but like Korea (or like Germany used to) they are devided by two different systems. Of course the major eye is on the 2nd ("American") war: Though America and his Allies fought heavily, the war was lost. A big reason was the American home-front with its peace movement,but the main cause for the loss of South Vietnam was South Vietnam itself. They thought the Americans would do the whole job themselves alone. America tried as hard as the could, but it was an unequal fight in many ways. The real losers of the war were the 18, 19, 20-year old boys, who were sent to a foreign, unknown country. Most of them didn't really know what they were fighting for, they just did what they were told to.
With a lot of interviews (with members of both sides) and a lot of realism, this series is probably the best Vietnam war documentary.