Many Union soldiers said if the war was to free the blacks they would have never volunteered. Of course everyone one was a conscript by 1863 and the EP.
So there are a lot of questions regarding that.
Yeah, but then there’s that song they sang while doing it, “as He died to make men holy let us die to make men free”.
About the only thing I can really settle on was the comment by, IIRC, Shelby Foote (what a great Southron accent!), in the Ken Burns documentary. “whatever started it diminishes to insignificance compared to what it accomplished. In a brief four years the pronoun used to refer to the US changed from plural to singular. Globally, universally, and without comment.”. Like he said, it is really quite an amazing thing when you think about it.