Italy was actually quite populated, and Rome had managed to integrate central Italy quite thoroughly, particularly during the 4th century (for example, see the Latin Wars). This demographic advantage coupled with the thorough political integration wrought over the centuries ensured Rome could survive Hannibal's onslaught. But make no mistake, the toll was hard. In that sense, it was the payoff of Rome's policies of integration in generations prior. Those who abandoned Rome mostly were recent conquests.

The Allies mostly remained as such, later on leading to the Social Wars (91-87 BCE).