During the course of the First Punic War, the Roman navy was massively expanded and played a vital role in the Roman victory and the Roman Republic's eventual ascension to hegemony in the Mediterranean Sea. In the course of the first half of the 2nd century BC, Rome went on to destroy Carthage and subdue the Hellenistic kingdoms of the eastern Mediterranean, achieving complete mastery of the inland sea, which they called "Mare Nostrum". The Roman fleets were again prominent in the 1st century BC in the wars against the pirates, and in the civil wars that brought down the Republic, whose campaigns ranged across the Mediterranean. In 31 BC, the great naval Battle of Actium ended the civil wars culminating in the final victory of Augustus and the establishment of the Roman Empire.