Fighting was deadly in the Iron Age.Many people died in the Iron Age so they built hillforts for a benefit of war the benefit of hillforts where they can shoot the enemies with bows and arrows from height above then finishing them off with swords and spears 

Iron is better because it’s stronger than bronze and cheaper and easier to find. Iron was better because it’s it’s better for taking cattle and attacking tribes and good for getting more iron for more tools then repeat the process. And that’s why iron is better then bronze and quite easier to craft.