The history of human civilization is inextricably linked to its ability to understand and shape metals. For thousands of years, the Bronze Age ruled the ancient world. Bronze, a clever alloy of copper and tin, was a reliable metal that was easily melted at a relatively low temperature and cast in clay or stone molds. This castability allowed for the mass production of uniform tools, vessels, and weapons, enabling great civilizations like Egypt, Mesopotamia, and the Indus Valley to build magnificent cities and organized armies upon its foundation. But bronze, for all its glory, had its inherent limitations: copper and especially tin mines were very rare and precious, and controlling them often led to bloody wars. Furthermore, bronze was a relatively soft metal that, under heavy blows, would bend instead of breaking, losing its effectiveness.
With the advent of the first millennium BCE, a new, more abundant, and more powerful metal called iron gradually found its place in the world. But this was not the tough steel we know. Ancient blacksmiths, with their primitive furnaces that were not much different from pottery kilns, could only heat iron ore to the point where it turned into a pasty, spongy mass called a "bloom." This mass was a combination of iron and numerous impurities. The blacksmith then had to spend hours hammering this hot mass with heavy sledges to separate the impurities as slag and obtain a relatively pure metal that we today call "wrought iron."
This process was incredibly arduous, time-consuming, and very costly. Producing an iron sword by this method took days and required a very high level of skill. The final product, although harder than bronze, would still bend and break under severe blows due to its low carbon content. This limitation was the biggest obstacle to the mass production of high-quality iron weapons and the full equipment of an army with this superior metal. Armies still used a combination of bronze and iron weapons, and iron was more a metal for the elite and officers than for ordinary soldiers.
The real revolution began with the invention of the blast furnace. This technology, which is used by Kourosh in our story, was a quantum leap in the history of metallurgy. The blast furnace was no longer a simple pit in the ground; it was a tower of stone or fire-resistant bricks, 3 to 5 meters high, that operated on a simple but ingenious principle: reaching the melting point of iron (about 1538 degrees Celsius). This temperature was far beyond what traditional furnaces could produce, and the key to achieving it was the precise control of raw materials and airflow.
The masterstroke of this process was the continuous and high-pressure blowing of air into the heart of the fire. Using giant blacksmith's bellows operated by human or animal power, which injected oxygen under pressure into the center of the furnace through clay nozzles, the temperature would rise exponentially. In this scorching heat, the limestone would melt and, like a chemical solvent, combine with the impurities in the iron ore (mainly silicates), forming a lighter substance called slag. Simultaneously, the purified iron would combine with the carbon in the charcoal and turn into liquid cast iron.
This molten iron, which collected at the bottom of the furnace due to its higher density while the lighter slag floated on top, was drained from a vent at the bottom of the furnace and poured directly into sand or clay molds. This direct casting capability was the greatest advantage of this technology. There was no longer a need for hours of hammering. Now, hundreds of completely uniform and high-quality spearheads, sword blades, or arrowheads could be made in a single day.
This technology was a true "secret weapon." Firstly, it allowed for mass production, enabling a kingdom to arm an army to the teeth with the best weapons of the day in a short time. Secondly, due to its higher carbon content, cast iron was much harder and more durable than wrought iron and had greater resistance to impact. And finally, this technology had a dual use; both for making deadly weapons and for producing agricultural tools like plowshares, which could increase grain production and allow for the feeding of larger armies and a greater population. This revolution of fire and iron changed not only the fate of wars but the course of civilization's history forever.