Background of the Greek War of Independence
The Fall of Constantinople in 1453 and the subsequent fall of the successor states of the Eastern Roman Empire marked the end of Byzantine sovereignty. Since then, the Ottoman Empire ruled the Balkans and Anatolia, although there were some exceptions: the Ionian Islands were under Venetian rule, and Ottoman authority was challenged in mountainous areas, such as Agrafa, Sfakia, Souli, Himara and the Mani Peninsula.
Source: Wikipedia — Background of the Greek War of Independence (CC BY-SA 4.0)