About 1500 BC, increasing numbers of smelted iron objects (distinguishable from meteoric iron by the lack of nickel in the product) appear in Mesopotamia, Anatolia, and Egypt.
Iron Working is the ancient form of work that many people in the days used as means of income. They would do this by working iron into various weapons and Armour.
Level 2 allows 10% increased defense
Level 4 allows a 10% increase in army defense. Now 40% from base.