Bardas belonged to the great family of the Skleroi, which owned enormous estates at the eastern outskirts of Asia Minor. His mother Gregoria descended from Basil I's brother Bardas. The greatest coup of his early career was a brilliant defense of Constantinople against the army of Svyatoslav I of Kiev in 970. During the Battle of Arcadiopolis, he reportedly managed to inflict as many as 20,000 casualties on the Rus, while the campaign claimed the lives of merely 25 Greek soldiers.
After he had shown himself equal to dealing with the fiercest enemies of Byzantium, Bardas became a trusted advisor to John I Tzimiskes, who was likewise of Armenian stock and his brother-in-law. Upon John's death, Skleros aspired to replace him as an acting emperor. The eunuch Basil Lekapenos, who actually led the imperial government, entertained other plans, however, deposing Bardas from his key post of general in the East in 976.
According to Michael Psellos, Skleros was "a man who was not only a competent planner, but extremely clever in carrying out his schemes, possessed of vast wealth (no mean asset in one who aimed at a throne), with the prestige of royal blood and of success in great wars, with all the military caste at his side to help on his enterprise."