In 849, when a Saracen fleet from Sardinia approached Portus, Leo IV summoned the maritime republics – Naples, Gaeta and Amalfi – to form a league. The command of the unified fleet was given to Cesarius, son of Duke Sergius I of Naples. Aided by a fierce storm, the Saracen fleet was destroyed off Ostia. The Battle of Ostia was one of the most famous in history of the Papacy of the Middle Ages and is celebrated in a famous fresco by Raphael and his pupils in his rooms of the Vatican Palace in the Vatican City.