My brother was in the Navy from 1965 to 1968. Viet Nam was just getting started for us when he enlisted. He spent most of his hitch floating on a small carrier between San Juan Puerto Rico and Panama City. Protecting NO ONE, defending NOTHING. At least, that's how HE summed it up.
I had other friends in other military branches who served THEIR time in "dangerous" defense of Hamburg, Biloxi, Norfolk, VA, and small towns in France and England. They, too went away with feelings of NOT having guarded or protected ANYthing THEY felt was vital to America.
Even the Viet Nam vets I know feel this way.."Since the foundation of the conflict", one said,"was a civil war between North and South Viet Nam, We were serving THAT country, INSTEAD of OURS!"
I've always saluted them because their INTENTIONS were honorable. And it wasn't THEIR fault their efforts were put to waste.