[shrinkermd]

Yes, I agree, but the conventional wisdom is we did lose the VietNam War. The MSM, colleges, universities and many others frequently refer to the war as lost, and I would guess that this has convinced the majority of the population of this view.

[Jeff Head]

I take every opportunity with my own kids, their friends, on forums, and in my conversations with anyone who indicates such a belief to educate tham as regards the truth.

[Captain Rhino]

Yes, “We” (the United States collectively) lost the Vietnam War. That is simply to state the obvious.

Your question asks how. There are a lot of different parts of the answer to that question. As a veteran of the war, I have my own opinions. But for a summary of the basic facts concerning the end of the Vietnam War, the wikipedia article is not bad:
http://en.wikipedia.org/wiki/Vietnam_war#Final_North_Vietnamese_offensive

At bottom, it is very difficult to defeat an opponent with effectively limitless material resources in critical war materials and a determination to win so strong that it will sacrifice substantial portions of its own population to secure victory. It is doubly difficult for the defender when he loses the material support needed to fight such an onslaught through the perfidy of its main ally.

Since the US Congress controlled the purse strings at the time, it must bear the lion's share of the responsibility for “losing” the war.

At the end, the South Vietnamese were poorly led militarily and politically. But this is just to say people can become confused and can panic in the midst of a existential crisis. Where they were properly equipped and lead (such as the 18th ARVN Divison defense at Xuan Loc), the South Vietnamese fought with skill and determination.