It's true that Washington and Lee would have considered such destruction barbaric according to the thinking of their times. Sherman might have considered it a necessary act. The thinking at the time of WWII was that in an era of industrial war civilian populations of workers were part of the ability of the enemy to continue to fight and thus were strategic targets. That said, it's my understanding that Hiroshima and Nagasaki were targeted because they had been untouched by previous conventional bombing, not because of their military significance. I believe that this was done to show the Japanese the horrifying cost of continued resistance.
Hiroshima and Nagasaki were not the United States sins, the destruction ended the war and given the thinking of the times were not barbaric acts.
On the "Judeo" part (since you cite the O.T.) le me say that one reason I can respect the present-day Israeli military, is that as far as I can see they have conducted themselves, under unrelenting pressure, in a manner that befits a soldier's honor. Very forceful, decisive and efficient in wiping out military targets; conscientious about sparing noncombatant life and values.
The point I made about God's direct orders stands. Collateral deaths aside --- that's a separate question ---He forbids the direct and deliberate killing of the innocent, by which we mean not "ontologically perfect," but in context, people who are either noncombatants, or combatants who have been disarmed, captured, or damaged to the point where they can no longer aggress.
As I said, I am not a pacifist. I do believe in fighting to defend our people and our Judeo-Christian Civilization--- what's left of it. The ongoing breaking down the objective moral order, whether under the banner of Unconditional War or Women's Right to You Know What, has purchased us the death of our Civilization by our own hand.