The Iron Age is conventionally defined by the widespread use of Iron tools and weapons, alongside or replacing bronze ones. The transition happened at different times in different parts of the world as the technology spread. Mesopotamia was fully into the Iron Age by 900 BC. Although Egypt produced iron artifacts, bronze remained dominant there until the conquest by Assyria in 663 BC. The Iron Age started in Central Europe around 500 BC, and in India and China sometime between 1200 and 500 BC.
Before the start of what can be considered an ‘Iron Age’ there would have been some sort of slow gradual transition, especially in the earlier cases. So there are many examples of iron artifacts being produced in small quantities in places that were still far from their Iron Age. The place and time for the discovery of iron smelting is not known, but archaeological evidence seems to point to the Middle East area, during the Bronze Age in the 3rd millennium BC. One of the earliest smelted iron artifacts found is a dagger with an iron blade found in a Hattic tomb in Anatolia, dating from 2500 BC. By about 1500 BC, increasing numbers of smelted iron objects appear in Mesopotamia, Anatolia, and Egypt. For example, nineteen iron objects were found in the tomb of Egyptian ruler Tutankhamun, who died in 1323 BC, including an iron dagger with a golden hilt and sixteen models of artisan tools.
Iron artifacts still remained a rarity until the 12th century BC. Although iron objects from the Bronze Age were found all across the Eastern Mediterranean, they are almost insignificant in numbers when compared to the quantity of bronze objects during this time. By the 12th century BC, iron smelting and forging, for weapons and tools, was common from Sub-Saharan Africa and through India. As the technology spread, iron came to replace bronze as the dominant metal used for tools and weapons across the Eastern Mediterranean. Iron working was introduced to Greece in the late 11th century BC and the earliest parts seeing the Iron Age in Central Europe are of the Hallstatt culture in the 8th century BC. Throughout the 7th to 6th centuries BC, iron artifacts remained luxury items reserved for an elite. This changed dramatically after 500 BC with the rise of the La Tène culture, from which time iron also becomes common in Northern Europe and Britain. The spread of iron working in Central and Western Europe at this time is heavily associated with the Celtic expansion.
In most of these places, as expected, the transition from Bronze to Iron as the dominant metal was very slow. To begin with Iron was actually a rather poor material for weapons, particularly early on when iron smelting knowledge was weak. Swords would be liable to bend or break. Yet bronze weapon manufacturing had been perfected after many centuries of use, so it would be more efficient and convenient to stay with the tried and tested. However there is an event which straddled the Bronze and Iron Ages, and may be part of an example of a more sudden change from bronze to iron. This event, known as The Late Bronze Age collapse was a transition in the Aegean Region, Southwestern Asia and the Eastern Mediterranean from the Late Bronze Age to the Early Iron Age that historians believe was violent, sudden and culturally disruptive. There are various theories put forward to explain the reasons behind the collapse, many of them based on Environmental and cultural factors.
There are also many theories that may show that it may be no coincidence that the collapse and the transition to Iron overlapped in this area. One suggests that iron, while inferior to bronze for weapons, was in more plentiful supply and so allowed larger armies of iron users to overwhelm the smaller bronze-using armies. Iron’s advantage was that its ores were very easily accessible. And while the smelting process was more difficult, once learned it would allow mass production of iron items. It didn’t matter if the bronze weapons were as good or better, if you could field ten times as many armed men. However, this argument has been weakened with the finding that the shift to iron may have occurred after the collapse instead of before. Another theory is that the disruption of long distance trade during and after the collapse cut the supplies of tin, making bronze impossible to make. Whichever way the Mediterranean cultures came to their Iron age, it was likely from here that Iron production techniques were passed on to eventually become the norm and gradually move north with the expansion of the Celtic cultures throughout Europe.