Huh? You claim that the Geneva Convention of 1864 contained all sorts of clauses preventing attacking cities, protecting property, and all the rest. I print the entire convention showing you're completely wrong and that becomesm 'boatloads of unrelated material'? You lied, there is nothing unrelated in that.
From the beginning of warfare to the advent of contemporary humanitarian law, over 500 cartels, codes of conduct, covenants and other texts designed to regulate hostilities have been recorded.
And how many of those existed prior to 1861? Name a few.
1864 Sherman would announce that "to the petulant and persistent secessionists, why, death is mercy."
Sherman also said, "War is the remedy our enemies have chosen. And I say let us give them all they want; not a word of argument, not a sign of let up, no cave-in until we are whipped - or they are." Sherman's tactics, while harsh, were effective and ended the war sooner. Sherman's tactics weren't a lot different than those practiced by Lee when he was in the North. If they were war criminals, then they were all war criminals together.