He and his followers took part in a war in Gaul, assisting the Arverni and Sequani to defeat their rivals the Aedui, after which they settled in large numbers in conquered Gallic territory in the Alsace region.

The Romans gave these divisions the term pagi ( from which comes the French word pays, " region "); these pagi were organized into civitates, which corresponded more or less with the pre-Conquest communities or polities sometimes described misleadingly as " tribes ," such as the Aedui, Allobroges, Bellovaci, and Sequani ( see List of Celtic tribes ).

These circumstances explain an apparent contradiction in Strabo, who in one sentence says that the Aedui lived between the Saône and the Doubs, and in the next, that the Sequani lived across the Saône ( eastward ).

They were nearly between their neighbors to the northeast, the Sequani, who occupied the Doubs river valley, and the Arverni in the Massif Central.

Caesar does not say what the cause of the conflict was, but the Sequani controlled access to the Rhine river along the valley of the Doubs.

Tradesmen headed up the Rhone and its tributary the Saône ( the ancient Arar ) could not pass the Doubs at Vesontio without coming to terms with the Sequani, nor could anyone pass from the Rhine to the Rhone except on similar terms.

Ariovistus made the decision to clear out the Sequani from the strategic Doubs valley and re-populate it with Germanic settlers.

The Saône formed their eastern border, separating them from the Sequani.

The Arar ( Saône ) River formed part of the border between the Haedui and their hereditary rivals, the Sequani.

" The Aedui and the Sequani fought each other to control the Arar ( now the Saône ) because the control of the river allowed taxation of all the Roman and Celtic products traveling to the north of the continent via the waterways.

Caesar moves his troops to Vesontio ( modern Besançon ), the capital city of the Sequani.

In historic times the town was first recorded in the journals of Julius Caesar, in his commentaries detailing his conquest of Gaul, as the largest town of the Sequani, a smaller Gaulic tribe ; Caesar gave the name of the town as Vesontio ( possibly Latinized ), and mentions that a wooden palisade surrounded it.

Upper Germania was occupied by Gaulish tribes including the Helvetii, Sequani, Leuci, and Treveri, and, on the north bank of the middle Rhine, the remnant of the Germanic troops that had attempted to take Vesontio under Ariovistus, but who were defeated by Caesar in 58 BC.

Strabo, who lived a generation after Caesar in the late republic and early empire, does make a statement concerning the cause of the conflict between the Sequani and Aedui, and it was in fact commercial, at least in Strabo's view.

The location of the final battle between the Aedui and their enemies, which Caesar names as the Battle of Magetobriga, remains unknown, but Ariovistus ’ 15, 000 men turned the tide, and the Aedui became tributary to the Sequani.

Caesar makes it clear that Germanic tribes were actually in the land of the Sequani and were terrorizing them.

Caesar reports that Ariovistus stated that " he was not so uncivilized nor so ignorant of affairs, as not to know that the Aedui in the very last war with the Allobroges had neither rendered assistance to the Romans, nor received any from the Roman people in the struggles which the Aedui had been maintaining with him and with the Sequani.

Julius Caesar also mentioned the wars that set the Aedui against the Arverni and the Sequani for hegemony over a large part of Gaul.

300 AD ), which comprised the territories of the Helvetii, Sequani and several smaller tribes.

The Helvetii now chose the more difficult northern route through the Sequani territory, which traversed the Jura Mountains, but bypassed the Provincia.

A map of Gaul in the 1st century BC, showing the relative position of the Helvetii and the Sequani

The Helvetii turned back and entered negotiations with the Sequani to let them pass in a peaceful manner.

Meanwhile, the Helvetii had already crossed the territories of the Sequani, and were busy pillaging the lands of the Aedui, Ambarri, and Allobroges.

Between the Helvetii and the Treveri around Trier, Strabo lists the Sequani, Mediomatrici ( around Metz ), the Leuci and the Lingones.

Dumnorix, Orgetorix of the Helvetii and Casticus of the Sequani were said to be conspiring to establish a Gallic triumvirate to replace the existing magistracies of the Gallic peoples shortly before Caesar's governorship.

In 58 BC, the first year of Caesar's governorship, Dumnorix used his influence to persuade the Sequani to allow the Helvetii to migrate through their territory.

The Sequani rewarded Ariovistus with land following his victory.

The Arar formed part of the border between the Aedui and the Sequani.

That move left the Sequani between him and the Jura mountains, not a tolerable situation for either if they were not going to be allies.

He was also party to a clandestine arrangement with Dumnorix of the Aedui and Casticus of the Sequani to seize control of their respective tribes by arms and between them rule most of Gaul.

The Celtic list between those points is Lingones, Remi, Mediomatrici, Sequani and Raurici.

This exodus was planned over three years, in the course of which Orgetorix conspired with two noblemen from neighbouring tribes, Casticus of the Sequani and Dumnorix of the Aedui, that each should accomplish a coup d ' etat in his own country, after which the three new kings would collaborate.

Some time before Caesar's governorship of Gaul ( which began in 58 BC ), the Gaulish Arverni and Sequani enlisted Ariovistus's aid in their war against the Aedui.

" The Sequani also habitually supported the Germans in their previous frequent expeditions across the river, which shows that Ariovistus ’ subsequent devastation of Sequani lands represented a new policy.

" But a worse thing had befallen the victorious Sequani than the vanquished Aedui, for Ariovistus, the king of the Germans, had settled in their territories, and had seized upon a third of their land, which was the best in the whole of Gaul, and was now ordering them to depart from another third part, because a few months previously 24, 000 men of the Harudes had come to him, for whom room and settlements must be provided.

But later the plan backfires as Ariovistus begins a violent takeover of the territory of the Arverni and Sequani, exercising a cruel tyranny over them.

When the Sequani, their hereditary rivals, with the assistance of a Germanic chieftain named Ariovistus defeated and massacred the Aedui at the Battle of Magetobriga, the Aedui sent Diviciacus, the druid, to Rome to appeal to the senate for help.

The Aedui ( allies of Rome ) are engaged in a power struggle with two other tribes called the Arverni and the Sequani.

At first the plan works because the German mercenaries help the Arverni and Sequani to oppress their enemy, the Aedui.

About 62 BC, when a Roman client state, the Arverni, conspired with the Sequani and the Suebi nation east of the Rhine to attack the Aedui, a strong Roman ally, Rome turned a blind eye.

The Sequani and Arverni sought Ariovistus ’ aid and defeated the Aedui in 63 BC in the Battle of Magetobriga.

Via council and parley, the Helvetic chieftain Orgetorix made negotiations with the ambitious Sequani and the Roman dominated Aedui.

The Arverni had once been the most powerful tribal hegemony in Gaul during the 3rd and 2nd centuries BC under their king, Luernios, but when his son ( or grandson ) Bituitus was defeated by the Romans in 121 BC, their ascendancy passed to the Aedui and Sequani.

Furthermore, it is known that the druids held high functions since Diviciacus came to Rome to plead the case of the Aedui during the Germanic invasion led by Ariovistus on the account of the Sequani.