The Later Iron Age (450 BCE-ca. 80 CE - "La Tène")


Around 450 BCE a major upheaval took place in the Celtic heartland. The main centers of princely power were violently destroyed. Since the Celts left no written records from this time we can't know for certain what happened, but it seems likely that the old, established aristocratic lineages were overthrown by other lineages who wanted access to the same profitable trade-routes. The centre of political and economic power in the Celtic world shifted a little to the north and west, to the area between the Marne and the Moselle (there was a secondary centre in Bohemia to the east).


In a way, the Celts had been destabilized by their very success. Increased availability of resources had led to a serious overpopulation of the Celtic heartland, forcing large numbers of people to seek homes beyond traditional Celtic borders. Sometimes entire tribal groups would migrate in this fashion. A prestigious and wealthy chieftain would surround himself with clients (_ambacti_) who swore fealty to him and accompanied him on his military expeditions in exchange for glory and plunder. In some cases they would settle down in a new territory; in others, they would remain landless mercenaries, serving the political interests of non-Celtic Mediterranean peoples. The latter situation may represent the origin of what mediaeval Irish literature calls _fianas_: unsettled warrior-fraternities surviving by hunting, plunder and mercenary engagements, independent of most of the institutions of mainstream Celtic society.


All these population movements resulted in a huge territorial expansion of the Celtic world. A combination of groups from the Rhineland and Bohemia took over virtually all of Italy north of Tuscany, so that the region came to be called Cisalpine Gaul. In 390 BCE they entered into conflicts with the Romans, and even succeeded in sacking the city of Rome -- an outrage the Romans never forgot. New arrivals from Gaul settled in northern Spain. To the east, groups hiving off from the Bohemian homeland established settlements in the Balkans, all the way across the Danubian plain to the Black Sea coast, and even beyond that to what is now Ukraine, while their northernmost advance led them to what is now southern Poland. One such group raided Greece in the early 3rd century BCE, and then alternately cooperated with or threatened the local communities until King Nicomedes of Bithynia gave them a territory in Asia Minor where they could settle permanently: this became Galatia, the area of Anatolia around present-day Ankara. Celtic mercenaries played a conspicuous role in many conflicts of the region: some even became auxiliaries of the Ptolemies in Egypt.


Despite the volatile political atmosphere, this was a period of increased self-confidence, cultural enrichment and creativity for the Celts. Celtic artists came under the influence of many different models from different cultures, yet they synthesized all these influences into a unique, instantly recognizable style of their own -- a vocabulary of fluid geometric forms we have come to see as fundamental to the tradition of "Celtic art". From the new wealth of symbolic motifs in this art (some of it traceable to Eastern models), one can deduce that it was also a time of intellectual and religious ferment, with new theological and ritual concepts coming to enhance or replace older forms. This is when we first begin to hear of the Druids as a class of philosophers, ritualists and juridical experts with enormous social prestige and power, educated in schools and organized in a network that transcended the narrow tribal boundaries of the Celtic world. Although they are only mentioned in relation to Gaul and Britain (where they reputedly had their origin and the greatest concentration of their power), they may have extended their influence over other Celtic areas as well. No doubt such an institution did a lot to promote religious speculation and debate and must have given rise to a great wealth of new mythological and ritual forms -- which we, unfortunately, cannot know in detail, since the Druids never used writing to record their teachings, relying instead on the traditional exercise of memory.


By the middle of the 3rd century BCE the Romans, who vividly remembered their humiliation in 390 BCE, began to grow more and more uneasy about their Celtic neighbors in Italy, whom they saw as a powerful, culturally alien people that could not be trusted. Between 225 and 123 BCE Roman military campaigns (often under the pretense of defending important Greek trading centers from supposed Celtic threats) succeeded in breaking Celtic political control over all of Spain, Cisalpine Gaul and the southern third of Transalpine Gaul (Gallia Narbonensis). Despite fierce opposition, all these areas were placed under Roman administration. Celtic institutions were replaced by Roman institutions.


By the turn of the 1st century BCE, then, Rome had become an overwhelming political presence in western Europe. Even those Celtic tribes that remained independent found their economic life shaped by Roman decisions. The southernmost tribes of Free Gaul -- the Aruerni and Aedui, for instance -- abandoned their monarchical system of government (the "sacred king" model) in favor of rule by magistrates elected for a single term (_uergobreti_). Some scholars have seen this as a yielding to Roman pressure: Republican Rome wanted to ensure that its trading partners had a political culture similar to its own (making them "safe" and predictable), and so encouraged an institution that was more or less based on the Roman concept of the consulate (cf. Cunliffe1997). This seems corroborated by the fact that rebellions against Roman rule often involved attempts to restore traditional monarchy. Around this time the same Gallic tribes began to concentrate their political and economic life in large walled towns (_oppida_).


Population shifts in northern Europe (probably in response to climatic changes) caused a large number of Germanic-speaking peoples to migrate into traditionally Celtic lands. This, of course, resulted in further conflict and instability. In 58 BCE Julius Caesar took advantage of the situation by providing military aid to some Celtic tribes against others, eventually using his presence on the field to establish Roman rule over the entirety of Gaul -- despite the powerful last-minute rebellion mounted against him by the Aruernian prince Vercingetorix. By 50 BCE (and despite some later, ineffective rebellions) Roman control over Gaul was completely secure, and many Gallic leaders had been persuaded to accept it.


Julius Caesar had invaded Britain during his Gallic campaign, but failed to conquer it. This was accomplished a century later (43-51 CE), under the reign of the emperor Claudius. Since the Druids, through their intertribal network, provided a sophisticated ideological resource for continuing to oppose Roman rule, it was in the interest of the Roman government to eliminate them, and the conquest of Britain (where the Druids' most prestigious training centers were) gave them the opportunity to do so. In 60 CE Suetonius Paulinus, the military governor of Britain, destroyed the great Druid centre on Mona (present-day Anglesey) and massacred the Druids there. This effectively put an end to Druid influence throughout most of the Celtic world, and removed one of the main obstacles to complete Romanization.


By the end of the 1st century CE, Ireland alone of all Celtic lands remained outside Roman control -- although the Irish traded with the Romans and were certainly in frequent contact with the Roman world. Nevertheless, because of its marginal position, Irish tradition remained somewhat conservative: the Druidic institution survived there, as did the "sacred king" model of territorial rule.

Archaeologists refer to the Late Iron Age as the "La Tène" period, after a site on the lake of Neuchâtelin Switzerland, where a large number of weapons and ornaments had been thrown into the water, apparently as a religious offering.