In 264 BC the states of Carthage and Rome went to war, starting the First Punic War. Carthage was a well-established maritime power in the Western Mediterranean; Rome had recently unified mainland Italy south of the Arno River under its control. Rome's expansion into southern Italy probably made it inevitable that it would eventually clash with Carthage over Sicily on some pretext. The immediate cause of the war was the issue of control of the Sicilian town of Messana (modern Messina).