The Helvetii were a tribe that originated from what is modern day Switzerland, who, prior to battle with Caesar, had been migrating through Roman Gaul. At Geneva, the Romans destroyed the wooden bridge across the Rhone and constructed nineteen miles of fortifications. The Helvetii tribe tried to migrate by another route, and were crossing the river Arar (Saône) using rafts and boats. Caesar was informed by his scouts and proceeded to engage the Helvetii. Three parts of the Helvetii forces had crossed the river and Caesar routed the fourth part left on his side of the river, killing a great many and driving the rest into the woods.