In the fifth century, the western half of the Roman Empire collapses, and the island of Corsica is invaded by the Vandals and the Ostrogoths.

It is briefly recovered by the East Romans (Byzantines).

it soon becomes part of the Kingdom of the Lombards: this makes it a dependent of the March of Tuscany, which uses it as an outpost against the Saracens.

Pepin the Short, king of the Franks and Charlemagne's father, expels these and the Lombards and nominally grants Corsica to Pope Stephen II.

In the first quarter of the eleventh century, Pisa and Genoa together free the island from the Arab danger.

After this the island comes under the influence of the republic of Pisa.The crushing defeat experienced by Pisa in 1284 in the Battle of Meloria against Genoa has among its consequences the end of the Pisan rule and the beginning of the Genoese influence: this is contested at the beginning by the King of Aragon, who in 1296 receives from the Pope the investiture over Sardinia and Corsica.

A popular revolution against this and the feudal lords, led by Sambucuccio d'Alando, receives the aid of Genoa.

after this, the Cismonte is ruled as a league of comuni and churches, after the Italian experience.

The following one hundred and fifty years are a period of conflict, when Genoese rule is contested by Aragon, the local lords, the comuni and the Pope: finally, in 1450 Genoa cedes the administration of the island to its main bank, the Bank of Saint George, which brings peace.

In the sixteenth century, the island enters the fight between Spain and France for supremacy in Italy.

In 1553, a Franco-Ottoman fleet occupies Corsica, but the reaction of Spain and Genoa, led by Andrea Doria, reestablishes Genoese supremacy on the island, confirmed by the Peace of Cateau-Cambresis.