Slavery was the main reason that the Southern leadership wanted to secede from the Union, and they were willing to go to war over their right to secede.
That seccession was the main reason that the Northern leadership was motivated, and they were willing to go to war to prevent the South's seccession.
Why was the north trying to prevent the south's succession?
And, if the north was so against slavery, why did the stars and stripes fly over slavery states for 85 years?
And, why did the northern states pass the Corwin Amendment?
