"Waste Deep in the Big Muddy"--Pete Seeger--Vietnam Then you could always go to "Ballad of the Green Berets" for the other side.

While we're looking at the other side, I've always sorta liked "The Bonnie Blue Flag" to present a Confederate point of view.

"The Man From Athabaska," from an album by Country Joe McDonald called "War, War, War," which is the WWI poetry of Robert W. Service set to music.

"Coming Around the Horn," and "Humbug Steamship Companies," by John Stone, from "Songs and Shanties of the California Gold Rush," by Dick Holdstock and Tom Murphy--written in the 1850's and '60's.