Many years have passed and still I wonder why
The worst of men must fight & the best of men must die.

That verse was actually composed by Fred Hellerman of The Weavers when the group recorded the song in the '50s. They deleted Woody's original final verse:

Now tonight there are lights in our country so bright
And in towns and in cities they are telling of this fight
Now our mighty battleships will steam the bounding main
And remember the name of the good Reuben James

As I seem to remember reading, they thought the original final verse sounded too pro-war.

Jay