The first Roman expedition outside mainland Italy was against the island of Sicily in 265 BC. This led to the outbreak of hostilities with Carthage, which would last until 241 BC. At the time, the Punic city was the unchallenged master of the western Mediterranean, possessing a long maritime and naval experience and a large fleet. Although Rome had relied on her legions for the conquest of Italy, operations in Sicily had to be supported by a fleet, and the ships available by Rome's allies were insufficient. Thus in 261 BC, the Roman Senate set out to construct a fleet of 100 quinqueremes and 20 triremes. According to Polybius, the Romans seized a shipwrecked Carthaginian quinquereme, and used it as a blueprint for their own ships. The new fleets were commanded by the annually elected Roman magistrates, but naval expertise was provided by the lower officers, who continued to be provided by the "socii", mostly Greeks. This practice was continued until well into the Empire, something also attested by the direct adoption of numerous Greek naval terms.