The Killer Angels by Michael Shaara

Speaking about Robert E. Lee:

"When Virginia left the Union she bore his home away as surely as if she were a ship setting out to sea, and what was left behind on the shore was not his any more. So it was no cause and no country he fought for, no ideal and no justice. He fought for his people, for the children and the kin, and not even the land, because not even the land was worth the war, but the people were, as wrong as they were, insane even as many of them were, they were his own, he belonged with his own. And so he took up arms wilfully, knowingly, in perhaps the wrong cause against his own sacred oath and stood now upon alien ground he had once sworn to defend, sworn in honor, and he had arrived there really in the hands of God, without any choice at all; there had never been an alternative except to run away, and he could not do that. But Longstreet was right, of course: he had broken the vow. And he would pay. He knew that and accepted it. He had already paid. He closed his eyes. Dear God, let it end soon."

I thought I'd let the book speak for itself.