I've been watching
this series on IPlayer. It's excellent, and I strongly recommend it to anyone with an interest in politics, as it's exploring how the leaders lied to and manipulated the public.
The bit where a veteran expresses his outrage that the President and his advisers knew that they were going to lose three years before he was sent to Vietnam is quite powerful. The briefing document from the mid 60s which states that the aims were 70% avoid humiliation, 20% resist communist expansion and only 10% improve the lot of the Vietnamese people is also particularly telling.
Watching the situation snowball and more and more people get killed because the politicians were protecting themselves rather than making decisions on the basis of what they knew the situation was is really depressing.