
It’s kind of interesting, the south pretty explicitly seceded over slavery but slavery was not initially the reason the north joined the war, that was unionism and their interpretation of the Constitution. It was only after the emancipation proclamation that the north used slavery as a rallying point. But yea overall it was about slavery
“Our new government['s] foundations are laid, its cornerstone rests upon the great truth, that the negro is not equal to the white man; that slavery—subordination to the superior race—is his natural and normal condition. This, our new government, is the first, in the history of the world, based upon this great physical, philosophical, and moral truth.” - Confederate VP Alexander Stephens