Humans have been at war continuously, at any given time, for centuries, if not millenia. And we create new weapons technologies continuously. The armored knights of 13th Century Europe would have been incomprehensible monsters to Greeks or Romans of the Classical Era. "Who could have so much metal? They must be Gods." Humans have been killing one another with great efficiency and enthusiasm since five minutes after we came down from the trees. We were annihilating cities before we had gunpowder or steel--ask the Carthaginians about that one.