Correct.  The South did not seek  to conquer the North.   It was a "War of Secession" .  Similarly, 1776 also began a war of secession.  There was no "American Revolution" as the colonists did not seek to conquer the British (the King had utterly failed in his contractual role as protectorate of the colonies, and allowed Parliament to enact taxation without representation).  

When one side is so loath to let the other side go that they literally go to war - that is a sure sign that there is some serious exploitation (and not just of the slaves - which were not all black).