What happened, in my very humbled opinion, in the western campaigns contributed a much needed "boost" of hope for Union objectives, and confidence to that aim. No one, at least I don't think Grant, had a clue as to what lay ahead. The Vicksburg campaign, I think above all, provided hope for the North, and new faith in their Western general. There are SO many layers here I can't possibly do justice for in a post like this, but I have to mention a lot of "luck" and strange behind the scenes problems were going on with Pemberton and his staff, and I think pride worked against CSA during Vicksburg campaign. But, I'm not too sure of anything. Learning more, though.