Everything depended on whether Picenum would hold out until Pompeius should come up to its defence. Already Caesar with his reunited army had penetrated into it along the coast road by way of Ancona. Here too the preparations were in full course; in the very northernmost Picenian town Auximum a considerable band of recruits was collected under Publius Attius Varus; but at the entreaty of the municipality Varus evacuated the town even before Caesar appeared, and a handful of Caesar's soldiers which overtook the troop not far from Auximum totally dispersed it after a brief conflict - the first in this war. In like manner soon afterwards Gaius Lucilius Hirrus with 3000 men evacuated Camerinum, and Publius Lentulus Spinther with 5000 Asculum. The men, thoroughly devoted to Pompeius, willingly for the most part abandoned their houses and farms, and followed their leaders over the frontier; but the district itself was already lost, when the officer sent by Pompeius for the temporary conduct of the defence, Lucius Vibullius Rufus - no genteel senator, but a soldier experienced in war - arrived there; he had to content himself with taking the six or seven thousand recruits who were saved away from the incapable recruiting officers, and conducting them for the time to the nearest rendezvous.
This was Corfinium, the place of meeting for the levies in the Albensian, Marsian and Paelignian territories; the body of recruits here assembled, of nearly 15,000 men, was the contingent of the most warlike and trustworthy regions of Italy, and the flower of the army in course of formation for the constitutional party. When Vibullius arrived here, Caesar was still several days' march behind; there was nothing to prevent him from immediately starting agreeably to Pompeius' instructions and conducting the saved Picenian recruits along with those assembled at Corfinium to join the main army in Apulia. But the commandant in Corfinium was the designated successor to Caesar in the governorship of Transalpine Gaul, Lucius Domitius, one of the most narrow-minded and stubborn of the Roman aristocracy; and he not only refused to comply with the orders of Pompeius, but also prevented Vibullius from departing at least with the men from Picenum for Apulia. So firmly was he persuaded that Pompeius only delayed from obstinacy and must necessarily come up to his relief, that he scarcely made any serious preparations for a siege and did not even gather into Corfinium the bands of recruits placed in the surrounding towns. Pompeius however did not appear, and for good reasons; for, while he might perhaps apply his two untrustworthy legions as a reserved support for the Picenian general levy, he could not with them alone offer battle to Caesar.
Instead of him after a few days Caesar came (14 Feb.). His troops had been joined in Picenum by the twelfth, and before Corfinium by the eighth, legion from beyond the Alps, and, besides these, three new legions had been formed partly from the Pompeian men that were taken prisoners or presented themselves voluntarily, partly from the recruits that were at once levied everywhere; so that Caesar before Corfinium was already at the head of an army of 40,000 men, half of whom had seen service. So long as Domitius hoped for the arrival of Pompeius, he caused the town to be defended; when the letters of Pompeius had at length undeceived him, he resolved, not forsooth to persevere at the forlorn post - by which he would have rendered the greatest service to his party - nor even to capitulate, but, while the common soldiers were informed that relief was close at hand, to make his own escape along with his officers of quality during the next night. Yet he had not the judgment to carry into effect even this pretty scheme.
The confusion of his behaviour betrayed him. A part of the men began to mutiny; the Marsian recruits, who held such an infamy on the part of their general to be impossible, wished to fight against the mutineers; but they too were obliged reluctantly to believe the truth of the accusation, whereupon the whole garrison arrested their staff and handed it, themselves, and the town over to Caesar (20 Feb.). The corps in Alba, 3000 strong, and 1500 recruits assembled in Tarracina thereupon laid down their arms, as soon as Caesar's patrols of horsemen appeared; a third division in Sulmo of 3500 men had been previously compelled to surrender.
Pompeius had given up Italy as lost, so soon as Caesar had occupied Picenum; only he wished to delay his embarkation as long as possible, with the view of saving so much of his force as could still be saved. Accordingly he had slowly put himself in motion for the nearest seaport Brundisium. Thither came the two legions of Luceria and such recruits as Pompeius had been able hastily to collect in the deserted Apulia, as well as the troops raised by the consuls and other commissioners in Campania and conducted in all haste to Brundisium; thither too resorted a number of political fugitives, including the most respected of the senators accompanied by their families. The embarkation began; but the vessels at hand did not suffice to transport all at once the whole multitude, which still amounted to 25,000 persons. No course remained but to divide the army. The larger half went first (4 March); with the smaller division of some 10,000 men Pompeius awaited at Brundisium the return of the fleet; for, however desirable the possession of Brundisium might be for an eventual attempt to reoccupy Italy, they did not presume to hold the place permanently against Caesar. Meanwhile Caesar arrived before Brundisium; the siege began. Caesar attempted first of all to close the mouth of the harbour by moles and floating bridges, with a view to exclude the returning fleet; but Pompeius caused the trading vessels lying in the harbour to be armed, and managed to prevent the complete closing of the harbour until the fleet appeared and the troops - whom Pompeius with great dexterity, in spite of the vigilance of the besiegers and the hostile feeling of the inhabitants, withdrew from the town to the last man unharmed - were carried off beyond Caesar's reach to Greece (17 March). The further pursuit, like the siege itself, failed for want of a fleet.
In a campaign of two months, without a single serious engagement, Caesar had so broken up an army of ten legions, that less than the half of it had with great difficulty escaped in a confused flight across the sea, and the whole Italian peninsula, including the capital with the state-chest and all the stores accumulated there, had fallen into the power of the victor. Not without reason did the beaten party bewail the terrible rapidity, sagacity, and energy of the "monster".
But it may be questioned whether Caesar gained or lost more by the conquest of Italy. In a military respect, no doubt, very considerable resources were now not merely withdrawn from his opponents, but rendered available for himself; even in the spring of 705 his army embraced, in consequence of the levies en masse instituted everywhere, a considerable number of legions of recruits in addition to the nine old ones But on the other hand it now became necessary not merely to leave behind a considerable garrison in Italy, but also to take measures against the closing of the transmarine traffic contemplated by his opponents who commanded the sea, and against the famine with which the capital was consequently threatened; whereby Caesar's already sufficiently complicated military task was complicated further still. Financially it was certainly of importance, that Caesar had the good fortune to obtain possession of the stock of money in the capital; but the principal sources of income and particularly the revenues from the east were withal in the hands of the enemy, and, in consequence of the greatly increased demands for the army and the new obligation to provide for the starving population of the capital, the considerable sums which were found quickly melted away. Caesar soon found himself compelled to appeal to private credit, and, as it seemed that he could not possibly gain any long respite by this means, extensive confiscations were generally anticipated as the only remaining expedient.