The instant the news of the defeat reached Rome, a levy of all males over seventeen years of age was ordered, and this produced another ten thousand men and a thousand cavalry.  Eight thousand slaves who were willing to serve were enlisted and armed, and four thousand criminals and debtors were released from prison and pardoned, on the condition of their taking up arms.  The praetor Marcellus was at Ostia with the ten thousand men with which he was about to embark for Sicily.

Thus Rome would be defended by forty-three thousand men, while Hannibal had but thirty-three thousand infantry, and his cavalry, the strongest arm of his force, would be useless.  From Cannae to Rome was twelve days’ march with an army encumbered with booty.  He could not, therefore, hope for a surprise.  The walls of Rome were exceedingly strong, and he had with him none of the great machines which would have been necessary for a siege.  He must have carried with him the supplies he had accumulated for the subsistence of his force, and when these were consumed he would be destitute.  Fresh Roman levies would gather on his rear, and before long his whole army would be besieged.

In such an undertaking he would have wasted time, and lost the prestige which he had acquired by his astonishing victory.  Varro, who had escaped from the battle, had rallied ten thousand of the fugitives at the strong place of Canusium, and these would be a nucleus round which the rest of those who had escaped would rally, and would be joined by fresh levies of the Italian allies of Rome.

The Romans showed their confidence in their power to resist a siege by at once despatching Marcellus with his ten thousand men to Canusium.  Thus, with a strongly defended city in front, an army of twenty thousand Roman soldiers, which would speedily increase to double that number, in his rear, Hannibal perceived that were he to undertake the siege of Rome he would risk all the advantages he had gained.  He determined, therefore, to continue the policy which he had laid down for himself, namely, to move his army to and fro among the provinces of Italy until the allies of Rome one by one fell away from her, and joined him, or until such reinforcements arrived from Carthage as would justify him in undertaking the siege of Rome.

Rome herself was never grander than in this hour of defeat; not for a moment was the courage and confidence of her citizens shaken.  The promptness with which she prepared for defence, and still more the confidence which she showed by despatching Marcellus with his legion to Canusium instead of retaining him for the defence of the city, show a national spirit and manliness worthy of the highest admiration.  Varro was ordered to hand over his command to Marcellus, and to return to Rome to answer before the senate for his conduct.