Around 1455, he was granted the title of Eristavi (duke) of Samokalako (Kutaisi, western Imereti, and the surroundings) by the Georgian king George VIII.
In 1463, Bagrat led a coalition of western Georgian nobles who met and defeated George VIII at the Battle of Chikhori.
Henceforth the Gelovani clan in Svaneti, the Shervashidze (Sharvashidze) in Abkhazia, the Dadiani in Odishi (Mingrelia), and the Vardanidze in Guria ruled as semi-independent princes.
To justify this step, he asked Michael IV, Patriarch of Antioch and Jerusalem, to compose a "Law of Faith" which stated that western and eastern Georgia had different history of conversion and, therefore, they should be independent from each other.
In 1477, Eristav of Odishi, Vameq II Dadiani opposed Bagrat's rule in Western Georgia, he then assembled the Abkhazians and Gurians and began the raids in Imereti.