 Complete the following phrase:  After his coronation in December 969, Tzimiskes dispatched his brother-in-law Bardas Skleros to subdue a rebellion by Bardas Phokas, a cousin of Tzimiskes who aspired to succeed their uncle as emperor. To solidify his position, Tzimiskes married Theodora, a daughter of Emperor Constantine VII. He proceeded to justify his usurpation by repelling the foreign invaders of the Empire. The tributary of Aleppo was soon assured under the Treaty of Safar. In a series of campaigns against the Kievan Rus encroachment on the Lower Danube in 970971, he drove the enemy out of Thrace in the Battle of Arcadiopolis, crossed Mt. Haemus, and 