Here's a Health To The Company by the Cheiftans is also a good one...dunno if it could be strictly called an anti-war song but it is rather sobering to listen to.

Chorus:

So here's a health to the company
And one to my lass
Let's drink and be merry
all out of one glass
Let's drink and be merry
all grief to refrain
For we may or might never
All meet here again