Nobody. At least not in this country. That is simply propaganda that people have been led to believe.
They fought a war to stop Independence for Southern States. They added "abolishing slavery" about two years after the war had already started.
Here is Abraham Lincoln's position on the subject as of August 22, 1862. He is perfectly willing to continue slavery at this point in the war.
Is it your contention that the South didn’t fight to preserve slavery?