C. Julius Caesar, Gallic War

The Helvetii had by this time led their forces over through the narrow defile and the territories of the Sequani, and had arrived at the territories of the Aedui, and were ravaging their lands. The Aedui, as they could not defend themselves and their possessions against them, send embassadors to Caesar to ask assistance, [pleading] that they had at all times so well deserved of the Roman people, that their fields ought not to have been laid waste-their children carried off into slavery-their towns stormed, almost within sight of our army. At the same time the Ambarri, the friends and kinsmen of the Aedui, apprize Caesar, that it was not easy for them, now that their fields had been devastated, to ward off the violence of the enemy from their towns: the Allobroges likewise, who had villages and possessions on the other side of the Rhone , betake themselves in flight to Caesar, and assure him that they had nothing remaining, except the soil of their land. Caesar, induced by these circumstances, decides, that he ought not to wait until the Helvetii, after destroying all the property of his allies, should arrive among the Santones.