After the victory of Caesar over the Helvetii, the tribes of Gaul made a general assembly under Caesars consent. The tribes from all Gaul sent ambassadors asking for Caesars good will. Among the supplicants came embassies from the Aedui, Sequani, and Averni led by the Aeduan Divitiacus, who begged Caesar for assistance against a foreign enemy.
The intensity of the conflict between the Sequani, Avernii and the Aedui, rivals in their quest for power over Gaul and its many Celtic tribes wore down each others forces to the point that they, in their desperation looked to foreign lands for aid in their power struggle. From the East the Sequani and Arverni employed the services of Germanic mercenaries under the powerful and talented leader known as Ariovistus.
Ariovistus was the king of the Suevi, the most powerful and largest of the German tribes. They were tall and hardy warriors, strong and savage, and disdained fear and all the other peoples. The land of the Suevi was said to be surrounded by desert wastes, having they devastated the land of all their neighbors.
The Aedui couldn’t withstand this new force, but when it seemed as if the Averni and Sequani were going to win this conflict, the now very well equipped and very experienced army of Ariovistus turned on their Celtic employers.
Ariovistus took their lands and everything of them, justified in the Germanic tradition of "right of conquest".
The Aedui now desperate and their lands being flooded with migrating bands of people such as the Helvetti, who were fleeing these dangerous new Germanic neighbors, asked their allies the Romans to come to their aid. Caesar saw this conflict as a perfect opportunity in his quest for glory and power.
Let the historians debate and bicker over who was the more righteous man with the most justified and noble intentions, What is known is that the negotiations between the Romans and the Germans put both parties on a course to war and that both Julius Caesar and Ariovistus were formidable generals with extremely skilled, powerful and well equipped armies.
For Julius Caesar, this would be no simple case of disciplined heavy infantry versus levies of barbarian tribesman, this would be a conflict with a professional fighting force, well equipped and in the opinion of Caesar, the most disciplined soldiers in all the world, the soldiers of Ariovistus. His Legionaries were indeed supposed to have been fearful of the reputation Ariovistus and his men had gathered, not just for their ferocity but also for their famously large physical stature, and for Ariovistus, he stood to lose everything he had gained, a man of his standing could not possibly have been unaware of the Roman military successes abroad, as well as their more recent successes against the migrating Helvetti, this would be a hard a fight for both parties, and both men and their soldiers would have been fully aware of this.
When it became clear that negotiations were not possible, conflict broke out. Ariovistus marched around Caesars flank and cut him from his base, but with another skillful march Ceasar could recover back his lines of communication with his base. Then, Caesar learned that Ariovistus was waiting for the full moon, under advice of his soothsayer, to begin an engagement and he took this opportunity to attack the Germans while they were low motivated.
The Roman soldiers attacked the Sweboz with confidence and a vigorous lust for slaughter, but the men of Ariovistus met them with a charge with such impetuosity that the Romans did not have the time to shift the ranks so as to cast all their javelins.
The Romans were put on a defensive stance, but they soon resumed their offensive habit and attacked with consummate courage, advancing boldly into the intervals and ranks of the enemy and tearing away their shields. After this, the left wing of the Sweboz was routed, but the enemy still held in the right. They were throwing back the Romans. Perceiving this danger, Publius Licinius Crassus made the third line of legionaries which lad lain in reserve. The shock of these fresh troops broke the enemy resistance.
Ariovistus and the Sweboz who managed to escape were in flight and had to cross the Rhine back to their land. Caesar pursued them making a bridge over the Rhine, but nothing more was heard about Ariovistus.