Off on a tangent here ..
According to a brief internet search, there were 2.7 - 3.1 million American military personnel, that were there, participating in the Vietnam war. If you include the non Vietnamese militaries, there were a lot more too.
Also, between 9 and 12 million people claim to have been there, participating in the Vietnam war.
I am guessing that half of the 9 - 12 million Americans that claim/claimed they were there, cannot prove they were there, because their service there was ... dum, dum, dum, dummmmmmmm, classified "TOP SECRET"!!!!
I get a chuckle, sometimes, about those classified claims. I had to have a TOP SECRET clearance before I could start my MOS training. My MOS school notebook was classified SECRET with a CODE WORD. But what I was training to be, was not classified.
What I did in Vietnam was not classified, just the product of the works was classified and nowadays, much of that has been declassified too. (for those that don't know and get upset with upper case words, the words CONFIDENTIAL, SECRET, and TOP SECRET, when properly used to classify a document, are always written in upper case font)