One of the worst stories I heard about armed combat was an SAS patrol. He was an avid bird watcher. He saw some Carrion vultures cruise down on a part of Yugoslavia. He thought:
"Why would they be there?"
Then he saw 2 men nailed to a wall in a cruciform position.
I know massacres have been going on for some time, but in the 1st World war things took a turn for the worse with chemical weapons. Before then men had to fight with chilvary.