For most of its history Rome was a regional power in central Italy. Three wars against Carthage in the third and second centuries BC turned it into the master of the Mediterranean.
Two rival powers
Carthage, a Phoenician city on the North African coast, commanded the western sea through trade and a formidable navy. As Rome expanded south, the two powers collided over Sicily. The First Punic War (264-241 BC) was fought largely at sea, and Rome (with no naval tradition) built fleet after fleet, losing thousands of ships to storms and battle before finally prevailing and taking Sicily as its first overseas province.
Hannibal in Italy
The Second Punic War (218-201 BC) produced Rome's most dangerous enemy: Hannibal. Rather than wait to be invaded, he marched an army (elephants and all) from Spain, over the Alps, and into Italy itself. For fifteen years he roamed the peninsula undefeated, crushing Roman armies at Lake Trasimene and, catastrophically, at Cannae in 216 BC, where tens of thousands of Romans died in a single afternoon.
Rome endures and answers
That Rome survived Cannae says much about the Republic's resilience: it refused to surrender, raised fresh armies, and wore Hannibal down while carrying the war to Spain and Africa. The young general Scipio, later called Africanus, finally forced Hannibal home and beat him at Zama in 202 BC.
Dominance, and a warning
The Third Punic War (149-146 BC) was less a contest than an execution: Rome besieged and destroyed Carthage utterly, selling its people into slavery and erasing the city. Rome now ruled the western Mediterranean. But the wars had also flooded Italy with wealth and slaves and given commanders long, glory-laden campaigns far from civilian control: pressures that would soon strain the Republic to breaking.