In 509 B.C. Carthage and Rome signed a friendship treaty. In 306, by which time the Romans had conquered almost the entire Italian peninsula, the two powers reciprocally recognized a Roman sphere of influence over Italy and a Carthaginian one over Sicily. But Italy was determined to secure dominance over all of Magna Graecia (the areas settled by Greeks in and around Italy), even if it meant interfering with the dominance of Carthage in Sicily.
Turmoil in Messana, Sicily, provided the opportunity the Romans were looking for. Mamertine mercenaries controlled Messana, so when Hiero, tyrant of Syracuse, attacked the Mamertines, the Mamertines asked the Phoenicians for help. They obliged and sent in a Carthaginian garrison. Then, having second thoughts about the Carthaginian military presence, the Mamertines turned to the Romans for help. The Romans sent in an expeditionary force, small, but sufficient to send the Phoenician garrison back to Carthage.
Carthage responded by sending in a larger force, to which the Romans responded with a full consular army. In 262 B.C. Rome won many small victories, giving it control over almost the entire island. But the Romans needed control of the sea for final victory and Carthage was a naval power.
With both sides balanced, the war between Rome and Carthage continued for 20 more years until the war-weary Phoenicians just gave up in 241.
According to J.F. Lazenby, author of The First Punic War, "To Rome, wars ended when the Republic dictated its terms to a defeated enemy; to Carthage, wars ended with a negotiated settlement." At the end of the First Punic War, Rome won a new province, Sicily, and began to look further. (This made the Romans empire builders.) Carthage, on the other hand, had to compensate Rome for its heavy losses. Although the tribute was steep, it didn't keep Carthage from continuing as a world-class trading power.
Online source: Frank Smitha The Rise of Rome
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