Titus Livius (Livy), The History of Rome, Book 27
Frank Gardner Moore, Professor Emeritus in Columbia University, Ed.

41. Hannibal, after concentrating the army which he had kept in winter quarters or garrisons in the land of the Bruttii, came to Grumentum¹ in Lucania, in the hope of recovering the towns which out of fear had gone over to the Romans. [2] The Roman consul hastened from Venusia to the same place, reconnoitring as he advanced, and pitched camp about fifteen hundred paces from the enemy. [3] The Carthaginians' earthwork seemed almost in contact with the walls of Grumentum; the distance was only five hundred paces. Between the Punic camp and the Roman lay a plain. [4] Bare hills overhung the left flank of the Carthaginians and the right flank of the Romans, without arousing [p. 375]suspicions for either army, because they had no woods nor² any hiding-places for an ambush. [5] In the plain between them charges starting from outposts brought on engagements not important enough to be mentioned. It was evident that the Roman general's only object was not to allow the enemy to get away. But Hannibal in his eagerness to make his way out of the place would go down into battle-line with all his forces. [6] Then the consul, using the enemy's talent, all the more readily that on such exposed hills ambuscades could not be feared, commanded five cohorts, with five maniples in addition, to cross over the ridge in the night, and to post themselves on the farther side of the hills. [7] As to the time for them to rise from ambush and attack the enemy he instructed Tiberius Claudius Asellus, tribune of the soldiers, and Publius Claudius, prefect of the allies, officers whom he was sending with them. [8] At daybreak he himself led out all his forces, infantry and cavalry, into battle-line. A little later the signal for battle was set up by Hannibal also, and a shout was raised in the camp as the men rushed in all directions to get their arms. Then cavalry and infantry in rivalry dashed out of the gates and, scattering over the plain, made haste to reach the enemy. [9] On seeing their disorder, the consul ordered Gaius Aurunculeius, tribune of the soldiers of the third legion, to send out the cavalry of the legion with all possible momentum against the enemy, saying that they had scattered so [10??] widely, like sheep, in disorder over the whole plain that they could be routed and crushed before they were drawn up in line.