Sure. I get what you mean: greek antiquity has records on the decision to exterminate an entire island of people. The capacity is absolutely there.
But I think a better perspective here is human history is one full of technological and social advances that resolve and prevent conflict. Even, yes, that unbagged atomic cat. It can be power for civilian use or it can be a bomb to burn their shadows into the concrete. War is when the actual prize of humanity: civility, breaks down.