Andronikos III Palaiologos's reign included the last failed attempts to hold back the Ottoman Turks in Bithynia and the defeat at Rusokastro against the Bulgarians, but also the successful recovery of Chios, Lesbos, Phocaea, Thessaly, and Epirus. His early death left a power vacuum that resulted in the disastrous civil war between his widow, Anna of Savoy, and his closest friend and supporter, John VI Kantakouzenos, leading to the establishment of the Serbian Empire.