C. Julius Caesar, Gallic War

There is a river [called] the Saone , which flows through the territories of the Aedui and Sequani into the Rhone with such incredible slowness, that it can not be determined by the eye in which direction it flows. This the Helvetii were crossing by rafts and boats joined together. When Caesar was informed by spies that the Helvetii had already conveyed three parts of their forces across that river, but that the fourth part was left behind on this side of the Saone , he set out from the camp with three legions during the third watch, and came up with that division which had not yet crossed the river. Attacking them encumbered with baggage, and not expecting him, he cut to pieces a great part of them; the rest betook themselves to flight, and concealed themselves in the nearest woods. That canton [which was cut down] was called the Tigurine; for the whole Helvetian state is divided into four cantons. This single canton having left their country, within the recollection of our fathers, had slain Lucius Cassius the consul, and had made his army pass under the yoke. Thus, whether by chance, or by the design of the immortal gods, that part of the Helvetian state which had brought a signal calamity upon the Roman people, was the first to pay the penalty. In this Caesar avenged not only the public but also his own personal wrongs, because the Tigurini had slain Lucius Piso the lieutenant [of Cassius], the grandfather of Lucius Calpurnius Piso, his [Caesar's] father-in-law, in the same battle as Cassius himself.