the Cartheginians who were, historically, Rome's supreme adversary.
After all, in reality the Carthaginians nearly destroyed Rome. When i frist played this game, i was expecting the Gauls to be sending huge hordes into the Alps, and the mighty Carthaginians invading Italy. Instead, i had gaul sending tiny little stacks of about 100 men which weren't cool, but just annoying and i had Carthage wiped out within 20 turns by the Scipii. Carthage didn't even gain territory, they continually lost it.