Kingdom of Sardinia and Aosta, dynastic possessions since the 11th century, the Principality of Piedmont (a possession built up in the 13th century), and the County of Nice (a possession since 1388). While in theory the traditional capital of the island of Sardinia and seat of its viceroys was Cagliari, the Piedmontese city of Turin was the "de facto" capital of Savoy. When the mainland domains of the House of Savoy were occupied and eventually annexed by Napoleonic France, the king of Sardinia made his permanent residence on the island for the first time in its history. The Congress of Vienna (1814–15), which
Sardinia Kingdom ended and Sardinia was returned to Roman rule. In 533, Sardinia returned to the rule of the Byzantine Empire when the Vandals were defeated by the armies of Justinian I under the General Belisarius in the Battle of Tricamarum, in their African kingdom; Belisarius sent his general Cyril to Sardinia to retake the island. Sardinia remained in Byzantine hands for the next 300 years aside from a short period in which it was invaded by the Ostrogoths in 551. Under Byzantine rule, the island was divided into districts called "mereíai" (μερείαι) in Byzantine Greek, which were governed by a