Hi Bubba,
During the 1980's WW2 films were not popular. However after the success of " Platoon " 1986 Best film of the year, Vietnam Films became popular. In the 1970's there were only a few film's on the Vietnam conflict, such as the Australian film " Odd Angry Shot " (about the Australians who fought in Vietnam), then I believe it was 1977 " Go Tell the Spartans " appeared about the early days of the war (1964) when Americans were there as advisors, and the war was just getting under way, until the attack in the " Gulf of Tolken " (sorry if there is a typo there). After that incident American began to send over troops. However the earliest war film I can recall about Vietnam other than some minor ones not considered war films, was a film called " Boys in Company C " with Lee J.Ermey (Best known for the Sargeant in " Full Metal Jacket." and actually a sargeant in Vietnam) Also in the 70's one of the best War related Films was " The Deer Hunter (1978) " with Robert Deniro.
A forum in his name is below... Also I put a ebay link to the movie " Boys in Company C " This film sold for big bucks a year ago and was long out of print, but with DVD they reprinted it and in VHS also. Grab it while you can get it.
Lee J. Ermey Forum
Boys Of Company C (ebay)