For centuries, the so-called Iberian peoples had established themselves in many Pyrenean valleys and neighboring plains, especially in the basins of the Gállego, Cinca, Segre, and Middle Ebro rivers. During the Iron Age, new invaders began to appear, whom we now know under the common name of Celts (Greek kéltoi, Latin celtae). This movement of Celtic peoples lasted several centuries. They were, of course, an Indo-European people.
One of the first Basque-Celtic contacts took place near the Garonne. Pliny and Plutarch attest that the Aquitanians repelled the Celts, forcing them to invade Spain by sea, landing on the western Cantabrian and Portuguese coasts. However, the truth is that, over the centuries, Celtic groups settled in the regions of Ger, Lannemezan, and Ariège: the Belendi.
From the detailed studies conducted by Professor Bosch Gimpera, an authority on the subject, it is clear that Celtic immigration took place in several phases. The first phase, led by the Celts from the Urns of southern Germany, took place 900 and 800 BC, extending north of the Pyrenees and reaching present-day Catalonia. In this phase, they reportedly infiltrated the Basque region of Aquitaine.
In the second phase, carried out in several stages, people arrived from central Germany, Holland, and Belgium. They entered through western France and penetrated the Basque Pyrenees. In the first phase, the Berones arrived, settling on the banks of the Ebro—the town of Briones in La Rioja might remind them. Other groups from this phase (700-650 BC) followed the Miranda-Pancorbo road to penetrate the Castilian plateau.
The arrival of the second stage groups, with a Germanic advance of Cimbri, is 650 and 600 BC. Around 600 BC, the Belgae arrived, from whom the Suessiones and Autrigones settled in Basque territory. According to Bosch Gimpera, part of the Germanic group of the Nerviones occupied various places along the road from Navarre to Pancorbo, infiltrating Basque territory among the Cantabrians and dominating the Castilian plateau and the Jalón Valley. These were the peoples later known as the Vaccaei and Arevaci.
The Celtic people traveled in caravans made up of families, flocks, belongings, and various animals. Conflicts with local peoples were sometimes resolved by arms and other times through agreements: free passage, temporary or permanent settlements, cession of pastures, lodgings, etc. Of course, the right bank of the Garonne remained in Celtic hands.
Some groups introduced through Roncesvalles reached Vardulia, occupying the Villarcayo region, where they built the fortress called Segontia Paramica (Sigüenza del Páramo) to defend themselves against the Coniscos, who had been evicted from those lands and forced to settle by the sea. Certain elements and loose groups managed to establish themselves in the Cantabrian and Vardulia lands of the interior, mingling with the natives.
The Berones settled permanently in La Rioja, forming a Basque-Celtic population with Basque nuclei in the most mountainous valleys. From Sos, Sause, the Suessiones, who had left small groups along the way from Roncesvalles to Miranda, lived. Another group was found in Etxauri (Navarre). The small group of Nervion settled in the Nervión River basin (not to be confused with the Ibaizábal River), which is their name.
The Garunni and Belendi moved into the mountain valleys through the Aquitanian Toulouse region. Evidence of Celtic culture has been found in lands bordering the present-day Basque Country. The pottery is characterized by decorations of parallel grooves or raised cords, present in Sena (Huesca), Roquizal del Rullo (Zaragoza), and Las Escondinas—all in the eastern Basque Country.
In Etxauri (Navarre), in the heart of the Basque Country, there is a Celtic necropolis that probably belonged to a Suession group established there. Celtic necropolises contain cremation tombs dug into the ground, where an urn holds the bones of the deceased. The Hallstatic Celtic culture of the Urnenfelder (urn ) appears at the end of the Pyrenean isthmus, in Catalonia.
In the 3rd century BC, Around the 5th century BC, some Iberian groups, driven by the Celts, migrated to Upper Aragon and, crossing the Pyrenees, entered Aquitaine. As a result of this Basque-Celtic conflict, the Basque Country suffered a serious setback. The best lands were occupied by the invaders. Aquitaine and Vardulia were the most affected. In the latter, the Autrigona tribe settled, mingling with the native population.
Vasconia lost lands occupied by the Berones, while the Ilergetes settled in large areas of Huesca. The Suessiones, established in areas of Sos and Sangüesa, erected defensive fortifications in Navardún and Berdún to protect themselves from the inhabitants of the Beral River and the Navarrese (the root "-dun" means "fortress").
Celtic power reached its peak in the 6th century BC, but by the 2nd century BC, they had already been absorbed into Euskal Herria. The banks of the Ebro and surrounding areas adopted important elements of Celtic culture. The balance indicates the Volcae, Ruteni, Belendi, and Garunni as the occupants of the right bank of the Garonne. The Tolosates are believed to have been the result of a mixture of Celts and Basques. On the left bank, peoples of Basque origin remained, mixed with Iberian elements: the Ubiskos, Tarusates, Auskis, Elusates, Onessis, and Taruskos.
From early historical times, the banks of the Garonne marked the separation the Celts (Gauls) and the Aquitanians (Basques). In the west of Euskal Herria, in the highest mountains by the sea, the Cantabrians consolidated their position. The coast up to the mouth of the Ibaizabal (Bilbao) remained in the hands of a mixed Basque-Celtic people: the Autrigones. The rest of the coast up to Bayonne was dominated by the Basque tribes: the Caristian, Varduli, and Vasconi. However, near the Adour, the Cocosates and Tarbelli were found, Celts who spread throughout the Landes and Béarn, especially in the lower reaches of the rivers.
In the upper basins, the Basque peoples continued to be the only inhabitants: Sibusates (Suletinos or Zuberotarras), Oskidates (Ossau), Biguerriones (Bigorre), and Vascones (Saint-Jean-Pied-de-Port). The Berones settled in the lower reaches of the Tirón, Glera, and Najerilla rivers. Some groups, such as the Suessiones, the Nerviones, and the Autrigones, were almost completely absorbed.
The upper Aragonese valleys remained Basque-speaking, even in language, although with assimilated Iberian elements, especially in the historic areas of Sobrarbe, Ribagorza, the Aran Valley ("sandy"), Pallars, Andorra ("Andosinos"), and Alto Urgell. On the southern side of the Pyrenees, Bosch Gimpera believes that the Pyrenean element remained intact in the Gergistani, while in the case of the Aussoceretes (Ripollés and Garrocha) and the Ausetanos (Vich and Gerona), there may have been some Celtic infiltration. In contrast, the coastal villages and the middle basin of the Segre River no longer bear traces of the earlier population.
In current Basque vocabulary, there are some reminiscences that could be related to the Celts, such as the names of the dolmens: triku-arri, trego-arri (which could recall the Autrikones or Autrigones); and armorkora and murko, also dolmens, which could refer to the "Armoricans" or Celtic Bretons. It is well known that invaders and foreigners are often given derogatory epithets, which would explain why murko ("rude person") is equivalent to triku ("unsociable person" or "hedgehog"). Murko also means "vessel, pitcher, jug."
The end result of the Celtic invasions was the formation of two powerful and dangerous peoples in the north and south of Euskal Herria: the Gauls and the Celtiberians.