Okay, well then let’s us just say it was the war to keep slavery in the South war. The South wanted to keep slaves and they attacked the North because of it. So the issue was the South wanted to keep slaves.
They did not attack the North to keep slavery. They stole federal property to keep the feds from doing fed things to them—for instance taxing—after secession. The theoretical war sparked by that incident, like I said, would have been different from the one we remember. The real war started because the feds decided to treat secession as an insurrection, and it was fought to force Southern states back into the union.
It was most emphatically NOT an invasion of North by the South to preserve slavery.