The Iron Age involved the adoption of iron smelting technology. It generally replaced bronze, and made it possible to produce tools which were stronger and cheaper to make than bronze equivalents. In many Eurasian cultures, the Iron Age was the last major step before the development of written language, though again this was not universally the case. It was not possible to mass manufacture steel because high furnace temperatures were needed, but steel could be produced by forging bloomery iron to reduce the carbon content in a controllable way. Iron ores were much more widespread than either copper or tin. In Europe, large hill forts were built either as a refuge in time of war, or sometimes as permanent settlements. In some cases, existing forts from the Bronze Age were expanded and enlarged. The pace of land clearance using the more effective iron axes increased, providing more farmland to support the growing population.

By 1000 BC - 500 BC, the Germanic tribes had a Bronze Age civilization, while the Celts were in the Iron Age by the time of the Hallstatt culture. Their cultures collided with the military and agricultural practices of the Romans, leading those Europeans who were conquered to adopt Roman technological advances.

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