Early human civilizations began to work metal toward the end of the Stone Age. The malleability of copper led to its becoming the first metal to be "tamed." Adding tin to copper created a much stronger alloy: bronze. This advance allowed for the crafting of tools and weapons of great durability. In turn, those improved tools made possible the working of iron, which soon replaced bronze as the metal of choice for tools and weapons.
In a Bronze/Iron Age society, advances in pottery, construction, and agriculture allow for the concentration of populations into larger and larger groups, with a corresponding upswing in the accumulation and sharing of knowledge. The rise of nations, citystates, and empires begins in the Bronze Age. Organized efforts to improve communications allow regional societies to exist. Galleys and small sailing vessels are capable of relatively long voyages, and some cultures may build extensive road or canal networks to link distant places. Improvements in agricultural efficiency permit the rise of artisans, craftsmen, professional soldiers, and other occupations that are not directly concerned with gathering food.
The sword replaces the club and the dagger as the preferred weapon of infantry. Chariots briefly dominate warfare before cavalry (aided by the introduction of the stirrup) renders chariots obsolete. The first true military forces or tactical systems appear. Armor can now be made from sewn plates or scales, metal links, or even forged breastplates, and a variety of metal melee weapons dominate the battlefield.