Hannibal at this period occupied with his veteran but much reduced forces the extreme south of Italy. It had not been expected either by friend or foe, that Hasdrubal would effect his passage of the Alps so early in the year as actually occurred. And even when Hannibal learned that his brother was in Italy, and had advanced as far as Placentia, he was obliged to pause for further intelligence, before he himself commenced active operations, as he could not tell whether his brother might not be invited into Etruria, to aid the party there that was disaffected to Rome or whether he would march down by the Adriatic Sea. Hannibal led his troops out of their winter quarters in Bruttium, and marched northward as far as Canusium. Nero had his head-quarters near Venusia, with an army which he had increased to forty thousand foot and two thousand five hundred horse, by incorporating under his own command some of the legions which had been intended to set under other generals in the south. There was another Roman army twenty thousand strong, south of Hannibal, at Tarentum. The strength of that city secured this Roman force from any attack by Hannibal, and it was a serious matter to march northward and leave it in his rear, free to act against all his depots and allies in the friendly part of Italy, which for the last two or three campaigns had served him for a base of his operations. Moreover, Nero's army was so strong that Hannibal could not concentrate troops enough to assume the offensive against it without weakening his garrisons, and relinquishing, at least for a time, his grasp upon the southern provinces. To do this before he was certainly informed of his brother's operations would have been an useless sacrifice; as Nero could retreat before him upon the other Roman armies near the capital, and Hannibal knew by experience that a mere advance of his army upon the walls of Rome would have no effect on the fortunes of the war. In the hope, probably, of inducing Nero to follow him, and of gaining an opportunity of outmanoeuvring the Roman consul and attacking him on his march, Hannibal moved into Lucania, and then back into Apulis;--he again marched down into Bruttium, and strengthened his army by a levy of recruits in that district. Nero followed him, but gave him no chance of assailing him at a disadvantage. Some partial encounters seem to have taken place; but the consul could not prevent Hannibal's junction with his Bruttian levies, nor could Hannibal gain an opportunity of surprising and crushing the consul. Hannibal returned to his former head-quarters at Canusium, and halted there in expectation of further tidings of his brother's movements. Nero also resumed his former position in observation of the Carthaginian army.