He wrote to the Mayor of Atlanta: ""You cannot qualify war in harsher terms than I will. War is cruelty, and you cannot refine it; and those who brought war into our country deserve all the curses and maledictions a people can pour out."
Since HE understood WAR, he won.
Understand the battle we are fighting, for Terri's life, for every life of people in similar circumstance. It is a war, and the most durable resolve to fight it is founded only in understanding of it.
Sherman won by being what was seen as cruel. Yet his ways tended to spare lives. His deep understanding -- to see the fundamental Hell that is war, allowed him to see that while in Hell, while an agent of Hell, he could at least be ruler of the Hell he commanded, and by that, save many, many, many lives. Which he did.
He could only master the ways in whcih he could direct hellish cruelity, but not make it less cruel.