The first major engineered metal alloy — copper alloyed with tin to produce something harder and more castable than either ingredient alone — whose adoption organized an age of long-distance trade, specialized elites, and palace kingdoms, and whose power was always hostage to the trade routes that carried its rarest ingredient.
Bronze is not found in the ground. Nobody mines bronze. Someone had to invent it — to discover that melting copper with a small addition of tin produces something neither metal is on its own: harder, tougher, and far easier to pour into a mold. That discovery was the first time in history that humans deliberately engineered a new material by mixing. The age it built, and the way it collapsed, tell us something permanent about the price of power built on scarce ingredients.