Iron Working allows the building of legions, a cheap offensive unit.
| Prerequisite advances:|
| Iron Working (Civ1)|
| Needed for further advances:|
Bridge Building, Gunpowder
Building on the experience of their Bronze Working, ancient smelters learned Iron Working, the manufacture and fabrication of a much more useful metal. Iron ore was extremely common compared to copper and tin, and Iron was harder, less brittle, and could hold a much sharper edge. It was an ideal material for tools and weapons. Some observers consider the development of Iron Working to have been a key step in the advance of civilization. It made workers much more efficient and was found useful in many new applications.