"... and it's 1,2,3, what are we fighting for? ..."

While some neocon chickenhawks like Bush and Rove and Cheney and Gingrich and Qualye will be happy to tell you exactly what great causes the US Government was fighting for in Indochina forty years ago, the only answer to the bipartisan American war that made any sense to anyone I knew was simple: FUCK IT.
Few people expressed that profound meditation on war and peace better than Country Joe McDonald with his "Feel Like I'm Fixin' to Die Rag" (preceded with the Fish Cheer) as performed here at Woodstock in 1969. I didn't have the pleasure of singing along there, but I vividly remember chanting and singing along with Joe and another very large crowd on the National Mall on 4/24/1971.
Enjoy.
 "Gimme an F!"
"Gimme a U!"
 
And, of course, like all the best sixties protest music, there's a great tie-in here to the Occupy Wall Street movement:

Well, come on Wall Street, don't move slow
Why man, this is war a-go-go.
There's plenty good money to be made
By supplying the Army with the tools of the trade,
Just hope and pray that if they drop the bomb,
They drop it on the Viet Cong.

Have fun following the bouncing ball. And singing along.

If you don't know this song by heart already, the American educational system is to blame. This is as important a part of our common cultural legacy as knowing the words to The Star Spangled Banner or Take Me Out to the Ballgame.