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

43. Meanwhile Hasdrubal, after abandoning the siege of Placentia, sent four Gallic horsemen and two Numidians with a letter to Hannibal. When they had already traversed nearly the whole length of Italy through the midst of the enemy, in following Hannibal as he withdrew to Metapontum they came by [2??] roads of which they were uncertain to Tarentum and were brought by Roman foragers who roamed about the country to Quintus Claudius, the propraetor. [3] At first they tried to confuse him by vague answers, but when the fear of torture was brought to bear and compelled them to admit the truth, they informed him that they were carrying a letter from Hasdrubal to Hannibal. [4] Together with the letter, still sealed as it was, they were turned over to Lucius Verginius, tribune of the soldiers, to be conducted to Claudius, the consul.¹ [5] At the same time two troops of Samnites were sent as an escort. When they had reached the consul, and the letter had been read by an interpreter and the captives questioned, Claudius thereupon judged that the [6??] situation of the state was not such that they should carry on the war by routine methods, each consul within the bounds of his own province, operating with his own armies against an enemy prescribed by the senate.² [7] Rather must he venture to improvise something unforeseen, unexpected, something which in the beginning would cause no less alarm among citizens than among enemies, but if accomplished would convert [p. 383]great fear into great rejoicing. [8] Sending³ Hasdrubal's letter to the senate at Rome, he likewise informed the conscript fathers what he was himself intending to do. In view of Hasdrubal's writing to his brother that he would meet him in Umbria,⁴ the consul advised the senate to summon a legion from Capua to Rome, to conduct a levy at Rome, to confront the enemy at Narnia⁵ with the city troops. [9] In such terms he wrote to the senate. [10] He sent also messengers in advance through the regions of Larinum, of the Marrucini, the Frentani, the Praetutii, along the line of his proposed march, that they should all carry from the farms and the cities provisions, ready for the soldiers to eat, down to the road, and should bring out horses and mules as well, that the weary might have no lack of vehicles. As for himself, out of the whole army he chose the best soldiers, citizens and allies, six thousand infantry, a thousand cavalry. [11] He announced that he intended to seize the nearest city in Lucania and its Carthaginian garrison; that they must all be ready for the march. Setting out at night, he changed his direction to that of Picenum.⁶

[12] The consul in reality was leading his army to his colleague by the longest of forced marches, having left Quintus Catius, his lieutenant, to command the camp.