With a lot of white guys dying to free slaves.
They didn't invade to free slaves. They invaded to reestablish Washington DC dominance over a section of the continent that did not want it.
That "Let's free the slaves" stuff didn't come until at least two years after the war had started. The original purpose of the war was to force the Southern states to keep paying 73% of the taxes for the nation as they had been doing for years before the war.