Titus Livius (Livy), The History of Rome, Book 31
Evan T. Sage, Ph.D. Professor of Latin and Head of the Department of Classics in the University of Pittsburgh, Ed.

21. The consular army had now moved from Arretium to Ariminum, and five thousand allies of the Latin confederacy from Gaul to Etruria. [2] Therefore Lucius Furius proceeded by forced marches from Ariminum against the Gauls who were still besieging Cremona, and bivouacked about a mile and a half from the enemy. [3] There was an excellent chance for a victory if he had attacked their camp immediately after his march; the Gauls had scattered through the neighbourhood without leaving a strong guard on duty. [4] But Furius spared his weary troops because he had made a strenuous march. [5] The Gauls, called back by the shouts of their comrades, dropped the booty which they had in hand and hurried back to their camp. The next day they moved out in battle-array, nor did the Roman refuse the engagement. [6] But the Romans had barely time to form inline, with such speed did the enemy advance to the attack. [7] The right squadron¹ —he had the allied army divided into squadrons —occupied the front line, with two Roman legions in reserve. Commanders were designated: Marcus Furius of the right squadron, Marcus Caecilius of the legions, Lucius Valerius Flaccus of the cavalry —all were lieutenants.² [8] The praetor kept with him two lieutenants, Gaius Laetorius and Publius Titinius, by whose aid he [9] planned to watch the whole engagement and meet all sudden attacks of the enemy. [10] At first the Gauls hoped, concentrating the mass of their [p. 63]force on one place, to be able to overwhelm and³ destroy the right squadron which was in the van. [11] When this did not succeed, they tried to outflank and envelop the enemy's line, a plan which seemed easy on account of their great numbers arrayed against a few. [12] When the praetor saw this, that he too might extend his front, he threw in two legions from his reserves on the right and left flanks of the front-line force and vowed a temple to Diiovis if he routed the enemy on that day.⁴ [13] He ordered Lucius Valerius to send the cavalry of two legions to one side against the flank of the enemy and to the other the allied cavalry, and not to allow the enemy to envelop his lines. [14] Seeing too that the Gallic centre was weakened by the extension of the line, at the same time he gave his men the order to charge in mass formation and to break through, and the flanks were thrown back by the cavalry, the centre by the infantry. [15] The Gauls, suffering heavy losses in every quarter, suddenly broke and in complete rout fled to their camp. [16] The cavalry pursued them in their flight, and presently the legions too followed and stormed the camp. Less than six thousand Gauls escaped; [17] more than thirty-five thousand were killed or captured, along with seventy standards and more than two hundred Gallic wagons laden with abundant spoils. Hamilcar⁵ the Carthaginian general and three noble Gallic commanders fell in the battle. [18] About two thousand of the captives from Placentia were recovered and restored to the colonists.