What younger folks may not realize
The army was not made up of volunteers during the Vietnam war. All men of the right age who were not 4-F were eligible to be drafted, and many, if not most, were. A few ran away to Canada and became fugitives to avoid going to 'Nam, but that had consequences, both legal and social. Most of the soldiers had no choice in being there, which had to have fueled their hatred of the enemy, especially as it was an unpopular war, and those who returned were not welcomed as heroes.
(Of course, rich people had ways of keeping their kids out of the army.)
Semper Contendere Propter Amoram et Formam