tetrarchy. David ruled the southernmost regions and led the defense of one of the most dangerous border areas, around Thessaloniki and Thessaly. The centres of his possessions were Prespa and Kastoria. Moses ruled from Strumitsa, which would be an outpost for attacks on the Aegean coast and Serres. Aaron ruled from Sredets, and was to defend the main road from Adrianople to Belgrade, and to attack Thrace. Samuel ruled northwestern Bulgaria from the strong fortress of Vidin. He was also to organize the liberation of the conquered areas to the east, including the old capital Preslav. Some records suggest that David played a major role in this tumultuous period of Bulgarian history. War with Byzantium After John I Tzimiskes died on 11 January 976, the Cometopuli launched an assault along the whole border. Within a few weeks, however, David was killed by Vlach vagrants and Moses was fatally injured by a stone during the siege of Serres. The brothers' actions to the south detained many Byzantine troops and eased Samuel's liberation of northeastern Bulgaria. A local Bulgarian uprising broke there, led by two boyars — Petar and Boyan, who became allies of the Cometopuli and submitted to their rule. The Byzantine army was defeated and retreated to Crimea. Any Bulgarian nobles and officials who had not opposed the Byzantine conquest of the region were executed, and the war continued north of the Danube until the enemy was scattered and Bulgarian rule was restored. After suffering these defeats in the Balkans, the Byzantine Empire descended into civil war. The commander of the Asian army, Bardas Scleros, rebelled in Asia Minor and sent troops under his son Romanus in Thrace to besiege Constantinople. The new Emperor Basil II did not have enough manpower to fight both the Bulgarians and the rebels and resorted to treason, conspiracy and complicated diplomatic plots. Basil II made many promises to the Bulgarians and Scleros to divert them from allying against him. Aaron, the eldest living Cometopulus, was tempted by an alliance with the Byzantines and the opportunity to seize power in Bulgaria for himself. He held land in Thrace, a region potentially subject to the Byzantine threat. Basil reached an agreement with Aaron, who asked to marry Basil's sister to seal it. Basil instead sent the wife of one of his officials with the bishop of Sebaste. However, the deceit was uncovered and the bishop was