Titus Livius (Livy), The History of Rome, Book 31
Cyrus Evans, Ed.

10. While every one's attention was turned to the Macedonian war, and at a time when people apprehended nothing less, a sudden account was brought of an inroad of the Gauls. [2] The Insubrians, Canomanians, and Boians, having been joined by the Salyans, Ilvatians, and other Ligurian states, and putting themselves under the command of Hamilcar, a Carthaginian, who, having been in the army of Hasdrubal, had remained in those parts, had fallen upon Placentia; [3] and, after plundering the city, and, in their rage, burning a great part of it, leaving scarcely two thousand men among the flames and ruins, passed the Po, and advanced to plunder Cremona. [4] The news of the calamity which had fallen on a city in their neighbourhood, having reached thither, the inhabitants had time to shut their gates, and place guards on the walls, that they might, at least, be besieged before they were taken, and send messengers to the Roman praetor. [5] Lucius Furius Purpureo, who had then the command of the province, had, in pursuance of the decree of the senate, disbanded the army, excepting five thousand of the allies and Latin confederacy; and had remained, with these troops, in the nearest district of the province about Ariminum. He immediately informed the senate, by letter, in what confusion the province was. [6] That, “of the two colonies which had escaped in the dreadful storm of the Punic war, one was taken and sacked by the present enemy, and the other besieged. [7] Nor was his army capable of affording sufficient protection to the distressed colonists, unless he chose to expose five thousand allies to be slaughtered by forty thousand [p. 1351]invaders (for so many there were in arms); and by such a loss, on his side, to augment the courage of the enemy, already elated on having destroyed one Roman colony.”