After Thessaly's ruler
John II Doukas (r. 1303–1318) died in 1318 without a male heir, the
Byzantine Empire moved to take advantage of the power vacuum in the region. Byzantine troops under
John Kantakouzenos occupied northern Thessaly, while the
Catalans of the
Duchy of Athens moved into the southern parts of the region. Central Thessaly became a battleground for the various local magnates, who competed with each other and called upon the two states for aid. One of those who turned to Byzantium for support was Gabrielopoulos, who possessed many estates in western Thessaly as well as in parts of southwestern
Macedonia, his lands reaching from
Trikala to
Kastoria. Sometime between 1318 and 1325, he acknowledged Byzantine
suzerainty and was given the title of
sebastokrator in return. He thus became the
de facto governor of much of Thessaly on behalf of the
Byzantine emperor, but preserving much local autonomy. His possessions included the towns and fortresses of Trikala,
Phanarion,
Stagoi,
Damasis, and
Elasson. After his death in 1332/3, however, his heirs began quarrelling amongst themselves, leading to an invasion by the
Epirote ruler
John II Orsini, while the Byzantines under
Andronikos III Palaiologos (r. 1328–1341) moved in and established direct control over the northern and eastern part of the region. With Orsini's death three years later, all of Thessaly came under Byzantine control. ==References==