Advances in military science and technology; an all volunteer military; 18 year olds are now adults instead of waiting until they are 21 years of age.
The non-politically correct answer is: As long as THEIR SON wasn't in Vietnam, it was business as usual.
everybody wanted an orgie. so the war was the only way they could get what they wanted. : )
Positives: Advances in military science Negatives: Casualties.
Thanks to lessons learned from Vietnam todays hi-tech jet aircraft still have cannons (guns) on them.
Use specialized troops for specialized wars.