Titus Livius (Livy), The History of Rome, Book 39
Evan T. Sage, Ph.D., Ed.

30. The same year the praetors in Spain, Gaius Calpurnius and Lucius Quinctius, when in the beginning of spring they had led their troops out of winter quarters and had united in Baeturia, marched into Carpetania, where the camp of the enemy lay, and prepared to conduct the campaign with a common plan and policy. [2] Not far from the towns of Dipo and Toletum a fight broke out between foraging parties, and as these were reinforced, each from its own camp, gradually all the troops were drawn out into the line. [3] In this sudden engagement both the familiar ground and the nature of the fighting favoured the enemy. The two Roman armies were routed and driven back into camp. The enemy did not keep up their pressure on the defeated foe. [4] The Roman praetors, in order that their camp might not be attacked the next day, in the quiet of the following night with silent signals¹ led the army away. [5] At daybreak the Spaniards approached the rampart in battle-line and entering an empty camp, contrary to expectations, plundered what had been left behind in the confusion of the night, and returning to their own camp remained quietly in their quarters for a few days. [6] About five thousand of the Romans and allies fell in the battle and rout, and with their spoils the enemy armed themselves. Then they moved away to the river Tagus. [7] Meanwhile the Roman praetors spent all their time in collecting [p. 313]auxiliaries from the allied towns of the Spaniards and² in restoring the courage of the men after the panic of the defeat. [8] When their strength was sufficient and even the soldiers were now demanding the enemy in order to wipe out the previous disgrace, they encamped twelve miles from the river Tagus. Thence, breaking camp in the third watch, they marched in a hollow square at dawn to the banks of the Tagus. [9] Across the river on a hill was the camp of the enemy. Immediately, where the river revealed fords in two places, Calpurnius on the right, Quinctius on the left, led the [10??] army across, the enemy quietly watching while they marvelled at their sudden advance and talked about how they might have caused confusion while the Romans were disorganized in the act of crossing the river. [11] Meanwhile the Romans, having brought over all their trains and massed them in one place, because they saw the enemy already in motion and there was no opportunity to fortify a camp, drew up their line of battle. In the centre were posted the fifth legion of Calpurnius and the eighth of Quinctius: these constituted the strength of the whole army. [12] They had an open plain as far as the camp of the enemy, free from any danger of ambuscade.