 At this time , and following the disastrous Battle of Acheloos in 917 , the Byzantines were mostly occupied in the Balkans against Bulgaria . Hence , Kourkouas 's first task as Domestic of the East was the suppression of the revolt of Bardas Boilas , the governor ( strategos ) of Chaldia , a strategically important area on the Empire 's northeastern Anatolian frontier . This was quickly achieved and his brother , Theophilos Kourkouas , replaced Boilas as governor of Chaldia . As commander of this northernmost sector of the eastern frontier , Theophilos proved a competent soldier and gave valuable assistance to his brother 's campaigns . 
