If we are talking about genuine atrocities on both sides, then the list is rather short, including items in my post #169 above.
Yes, some claim 50,000 civilians died total, but actual records of such numbers are non-existent.
Actual records support a few dozen here, maybe a hundred there, nothing remotely close to the total suggested.
All this in stark contrast to the millions killed in other civil wars.
As to what, exactly, was or was not considered a "war crime", we can surely judge what our ancestors thought "criminal" by the men they tried and executed for war crimes after the war.
There was one: a Confederate guerilla named Champ Ferguson, of Nashville, Tennessee who was hanged on 53 counts of murder, many said to be arbitrary & gruesome.
Those were murders he personally committed, not that he ordered, or wink-winked the other way as his men committed.
Here's my point: angry as the Union was at Confederates after the war, they did not hunt down & hang mass numbers for real or alleged "war crimes".
Just one man, Champ Ferguson.
Of course, if you wish to apply today's standards, that's a different subject, but then, what are you going to do about hundreds of thousands of WWII Allied bomber crews who destroyed Axis power cities?
I don’t disagree with your point. From a contemporary point of view, there’s no doubt that very few on either side were truly thought of as war criminals. (BTW you also forgot about Maj. Henry Wirz, the commander of Andersonville Prison in Georgia who was executed after the war for the murder of Union POW’s held there). However, from a moral point of view, it makes sense to consider the question. The intentional targeting of civilians is considered to be a war crime by today’s standards. Sherman undoubtedly engaged in such conduct, so he did commit war crimes. I am only considering the question as a moral one, certainly not as a practical matter. What the heck would we do to Sherman anyway if we did come to the consensus that he committed war crimes?
As for the bomber crews, I think you can give them a pass, but possibly hold their leaders responsible to some degree. Targeting factories or other facilities that produce goods for the enemy’s war effort is considered legitimate under the laws of war. Thus, for instance, bombing a factory or sinking a merchant ship carrying war material is legitimate military activity. Unless I am mistaken, bomber crews were never ordered to “go and destroy Dresden”, but rather, “destroy the munitions factory in Dresden.” This is an important distinction for whether or not to hold the crews themselves responsible. The fact that the bombers were not precise enough to destroy only the factory without collateral damage was not the crews’ problem. The leaders undoubtedly hid behind this fact to conceal their true intention, which was certainly the destruction of the city itself. Again, as a practical matter, I would have not expected prosecution of personnel in Allied air commands, but the argument for their responsibility can be made.