 Complete the following phrase:  The last major campaigns of the Roman navy in the Mediterranean until the late 3rd century AD would be in the civil wars that ended the Republic. In the East, the Republican faction quickly established its control, and Rhodes, the last independent maritime power in the Aegean, was subdued by Gaius Cassius Longinus in 43 BC, after its fleet was defeated off Kos. In the West, against the triumvirs stood Sextus Pompeius, who had been given command of the Italian fleet by the Senate in 43 BC. He took control of Sicily and made it his base, blockading Italy and stopping the politically crucial supply of grain from Africa to Rome. After suffering a defeat from Sextus in 42 BC, Octavian initiated massive naval armaments, aided by his closest associate, Marcus Agrippa: ships were built at Ravenna and Ostia, the new artificial harbor of Portus Julius built at Cumae, and soldiers and rowers levied, including over 20,000 manumitted slaves. Finally, Octavian and Agrippa defeated Sextus in the 