This is not to say that he is not also a war criminal. Far from it. This is only to say that, as Clauswitz pointed out over a century ago, war is politics by other means. This is the nature of politics. Winners write the history.
Losers have no choice.
Don't believe for one moment that America's own civil war was not fought with ruthless brutality by both sides. By historical standards as well as by the standards of the day, it was a particularly brutal war. War without atrocities is impossible. War itself is an atrocity. All wars are fought with ruthless brutality by both sides.