They didn’t care about the slaves. Aside from killing about 40,000 slaves and free blacks, during the Civil War, the North proceeded to kill about half a million after the Civil War by abandoning the South to starvation after destroying their land.
I personally reject any idea of the claim that the Civil War was fought to free slaves. You don’t starve 500,000 now ex-slaves after the war if your claim was to free them.
It was all about the land and, I believe, securing a permanent floor price for cotton domestically.
Thier were penalties for trying to rend the United States.