Your and Gianni's points can't be made often enough.
Lincoln's theory of the war was that he was acting as a constitutional officer of the Union in defense of same, and that everything he did was justified by his constitutional powers to suppress insurrection (pace for the moment the argument that secession wasn't insurrection).
And yet, as your quote of Stromberg shows, Lincoln then turned to one of the most dangerous creatures on earth, a German totalitarian romantic, to write a "pseudo-Hegelian waffle" justifying, as James Seddon dourly noticed, Union "warring-down" tactics after the fact.
What resulted resembles nothing in American political theory, and just reading it as posted (thanks to nolu chan, who keeps bringing these things concretely to our attention and forbidding our interlocutor to keep up his favored tactic of referring to them in the comfy-gauzy Lincolnian abstract) one has to wonder whether Washington and Jefferson wouldn't spin in their graves to hear such a document read out.
Bet it wouldn't bother Hamilton much, though. He was a broken-eggs kind of guy, just like Lincoln.
Finally, that was an excellent shot you excerpted at totalitoady James McPherson, performing his Squealer portrayal in panegyricising Lincoln's compassion.
free the southland,sw