Titus Livius (Livy), The History of Rome, Book 34
Evan T. Sage, Ph.D. Professor of Latin and Head of the Department of Classics in the University of Pittsburgh, Ed.

14. At midnight, after taking the auspices in due form, he set out, that he might choose the place he wished before the enemy was aware of his coming, led his troops beyond the camp of the enemy, and at daybreak, drawing up his line of battle, he sent three cohorts close to the very rampart. [2] The barbarians, marvelling that the Romans had appeared in their rear, themselves ran to arms. [3] Meanwhile the consul harangued his troops: “Nowhere, soldiers, is there any hope except in your courage, and I have deliberately acted so that there should be none. [4] Between us and our camp is the enemy, and in the rear is the enemy's country. What is most glorious is also the safest: to place our hopes in valour.” After this he ordered the cohorts recalled, to draw the enemy out of their camp by the pretence of flight. [5] What he had anticipated occurred. Thinking that the Romans were retreating in terror, they rushed out of the gate and filled with soldiers all the space that was left between the camp and the enemy's battle-line. [6] While they were in the confusion of forming their array, the consul, who had everything already prepared and in order, fell upon them in their disorder. The cavalry was the first to enter the battle on both flanks, but on the right they were at once repulsed, and retiring in fear they even caused a panic among the infantry. [7] When the [p. 455]consul observed this, he ordered two picked cohorts¹ to march around the right flank of the enemy and to show themselves in the rear before the infantry masses clashed. [8] The alarm which thus confronted the enemy equalized the disadvantage caused by the flight of the Roman cavalry; but so greatly had the infantry and cavalry on the right flank been thrown into confusion that the consul himself seized with his hand some of them and turned them around to face the enemy. [9] And so, as long as the fight was being carried on with missiles, the issue was uncertain; on the right, where the panic and flight had begun, the Roman resisted with difficulty, while on the left and in the centre the barbarians were hard pressed and looked [10] back with dread at the cohorts which were coming up in their rear. When they drew their swords after hurling their darts and javelins, then the battle, so to speak, took on new life. [11] For they no longer received unexpected random wounds from a distance, but closing foot to foot put all their hope in courage and in strength.