110 BATTLE OF THE METAURUS.
which Hannibal had constructed were found by Hasdrubal still in existence, and materially favored the speed of his advance. He thus emerged into Italy from the Alpine valleys much sooner than had been anticipated. Many warriors of the Ligurian tribes joined him; and, crossing the River Po, he marched down its southern bank to the city of Placentia, which he wished to secure as a base for his future operations. Placentia resisted him as bravely as it had resisted Hannibal twelve years before, and for some time Hasdrubal was occupied with a fruitless siege before its walls.
Six armies were levied for the defense of Italy when the long dreaded approach of Hasdrubal was announced. Seventy thousand Romans served in the fifteen legions, of which, with an equal number of Italian allies, those armies and the garrisons were composed. Upward of thirty thousand more Romans were serving in Sicily, Sardinia, and Spain. The whole number of Roman citizens of an age fit for military duty scarcely exceeded a hundred and thirty thousand. The census taken before the commencement of the war had shown a total of two hundred and seventy thousand, which had been diminished by more than half during twelve years. These numbers are fearfully emphatic of the extremity to which Rome was reduced, and of her gigantic efforts in that great agony of her fate. Not merely men, but money and military stores, were drained to the utmost; and if the armies of that year should be swept off by a repetition of the slaughters of Thrasymene and Cannae, all felt that Rome would cease to exist. Even if the campaign were to be marked by no decisive success on either side, her ruin seemed certain. In South Italy, Hannibal had either detached Rome's allies from her, or had impoverished them by the ravages of his army. If Hasdrubal could have done the same in Upper Italy; if Etruria, Umbria, and Northern Latium had either revolted or been laid waste, Rome must have sunk beneath sheer starvation, for the hostile or desolated territory would have yielded no supplies of corn for her population, and money to purchase it from abroad there was none. Instant victory was a matter of life or death. Three of her six armies were ordered to the north, but the first of these was required to overawe the disaffected Etruscans. The second army of the north was pushed forward, under Porcius, the praetor, to meet and keep in check the advanced troops of