Success is so much sweeter to those who have never experienced succeeding. In order to enjoy to the good times in life you must be hurt every once in a while along the way.
The 'purple host' is the royal army, Northern forces who defeated the Confederate armies. They took the flag which shows victory and triumph in battle. Do they truly feel as if they won though? Did either side really win?
Men lie deceased among the battlefield don't deserve to hear the sound of triumph since they have been defeated. Off in the distance you can hear sounds of cheers, celebration, triumph which makes way across the land. They have been victorious.
"Requires sorest* need" *sorest means physically painful or sensitive wound, hurt
"Not one of all the purple Host* Who took the Flag** today" *royal army, Northern forces defeated the Confederate army, **taking the flag shows victory in battle
"As he defeated- dying - On whose forbidden ear" Men lie dead and defeated on the battlefield, and since the have lost the don't deserve to hear the sound of triumph and victory.