The North invaded the South to push them back into the union. They were not of the mind to have to deal with a separate country that would probably split again, and again...hence my Gen. W. T. Sherman quote: "If the United States submits to a division now, it will not stop, but will go on until we reap the fate of Mexico, which is eternal war."
I think that sums up what I have said all along.
Kevin Dally