Relations between Rome and Carthage were cordial for a long time, in fact as long as the Greek domination of the Mediterranean world lasted. Indeed, trade agreements were concluded in -508, -348 and -306, as well as a mutual defense treaty in -279. In addition, Carthage sent a fleet in -279 to Ostia to support the Romans against Pyrrhus. But in the middle of the 3rd century BC. J.-C., the Greeks are definitively removed from the Western Mediterranean, because they are now under the domination of the successors of Alexander the Great (himself died in -323), king of Macedonia. Their convergent interests having thus disappeared, the two rival cities find themselves alone face to face.
The Romans note that Carthage has a considerable lead:from the shores of Africa through a good part of Hispania, the Punic city has many territories. But above all, all the islands of the Tyrrhenian Sea are Carthaginian (Corsica, Sardinia, Balearic Islands). And the completion of the conquest of Sicily by the Carthaginians would put all of southern Italy within their reach, and the Carthaginians could be at the gates of Rome in ten days. They must therefore make a decision to protect Italy, and have little option but war.