The North, of course.
“The North, of course (was fighting to destroy constitutional slavery).
That is an interesting comment.
Contrast this with the fact that President Lincoln took an oath (twice) to protect and defend the pro-slavery United States Constitution. As president you would expect him to defend the constitution.
Now you tell me Lincoln took up arms to violently overthrow the pro-slavery United States Constitution. If he did, you can scarcely say it was the Confederates that were in rebellion.