He succeeded upon the death of his father, Alexander II, and faced repeated assaults from the Ottoman Turks as well as the conflicts with his ostensible vassal princes of Mingrelia, Guria, and Abkhazia who were frequently joining the enemy.

After the Ottoman army left Imereti, Bagrat launched a program of restoration, reorganized the church, and enforced a law condemning to death all who engaged in slave trading practiced by the Turks in conjunction with some Georgian nobles.

At the Battle of Murjakheti near Akhalkalaki, Bagrat defeated and captured Qvarqvare III Jaqeli, prince-atabeg of Samtskhe, and annexed a bulk of his possessions to Imereti.

At the request of Qvarqvare’s son Kaikhosro, the Ottoman army invaded Imereti, only to put to flight by Bagrat and his ally Rostom, prince of Guria.

The prince of Mingrelia, Levan I Dadiani, however, defied Bagrat’s call to arms, and later sided with the Ottomans, even traveling to Istanbul, where he received gifts and assurances of protection.