Originally the Romans were not interested in the western Mediterranean

Originally the Romans were not interested in the western Mediterranean. They were not a naval power and their horizon was limited to her control over central and southern Italy. Rome gained dominance in the western basin of the Mediterranean as a result of winning the Three Punic Wars (264-241 BC, 218-201 BC and 149-46 BC) between Rome and Carthage, not an interest in controlling this area. 

The First Punic War was precipitated by Rome's decision to support mercenaries (the Mamertines) who had seized the city of Messana (in eastern Sicily, by the strait with the mainland) and to besiege and force into an alliance Syracuse (which had attacked the Mamertines) the most powerful of the Greek city-states of eastern and southern Sicily. This caused the Carthaginians, who had four ports in western Sicily, to mobilise for war. It is thought that the Romans were concerned that the tensions caused by the Mamertines could lead to a war between Carthage and Syracuse and that a victorious Carthage could seize eastern Sicily, which was by the Roman-controlled mainland. The situation turned into a struggle over the control of this island.

The Second Punic War was started by Hannibal, a Carthaginian general and the ruler of the Carthaginian territories in southern Spain, who invaded Italy. Rome won this war and took over the Carthaginian territories in Spain. The next door neighbours of Carthage, the Numidians of Algeria, who had been her allies, defected and went over to the Romans. At this point Rome dominated the western Mediterranean.

The Third Punic War was caused by the desire of a war party in Rome to destroy Carthage because of the animosity which Hannibal's invasion of Italy had caused and because there were fears of a resurgence in the economic and military power of Carthage.

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