History of Corsica various Italian republics that arose began to assume responsibility for the security and prosperity of Corsica, starting with Tuscany, the closest. Corsica was finally removed from the fighting by annexation to the Papal States in 1217. Pisa retained control of the island during most of the Middle Ages but at the start of the Renaissance it fell to Genoa in 1284, following the battle of Meloria against Pisa. Corsica successively was part of the Republic of Genoa for five centuries. Despite take-overs by Aragon between 1296–1434 and France between 1553–1559, Corsica would remain under Genoese control until the Corsican Republic
Corsica was divided in "pagi", which in the Middle Ages became the "pievi", the basic administrative units of the island until 1768. During the diffusion of Christianity, which arrived quite early from Rome and the Tuscan harbors, Corsica was home to many martyrs and saints: among them, the most important are Saint Devota and Saint Julia, both patrons of the island. Corsica was integrated into Roman Italy by Emperor Diocletian (r. 284-305). In the 5th century, the western half of the Roman Empire collapsed, and the island was invaded by the Vandals and the Ostrogoths. Briefly recovered by the Byzantines, it