Rome expanded beyond the borders of Italy by conquering much of the Mediterranean region, including fighting a series of three wars (Punic Wars, McKay et al., p. 151) with a fierce Mediterranean rival, the Carthaginians.
The Second Punic War was a major turning point for Rome and its continued overseas expansion. The Romans drove the Carthaginians out of Spain, and then attacked Carthage itself. The Romans, led by Scipio Africanus, defeated the Carthaginians,