War against the Bulgarian

The traditional struggle with the See of Rome continued, spurred by the question of religious supremacy over the newly Christianized Bulgaria. This prompted an invasion by the powerful tsar Simeon I in 894, but this was pushed back by the Byzantine diplomacy, which called on the help of the Hungarians. The Byzantines were in turn defeated, however, at the Battle of Bulgarophygon (896), and obliged to pay annual subsides to the Bulgars. Later (912) Simeon even had the Byzantines grant him the crown of basileus of Bulgaria and had the young emperor Constantine VII marry one of his daughters. When a revolt in Constantinople halted his dynastic project, he again invaded Thrace and conquered Adrianople.[56A great imperial expedition under Leo Phokas and Romano Lekapenos ended again with a crushing Byzantine defeat at the Battle of Anchialus (917), and the following year the Bulgars were free to ravage northern Greece up to Corinth. Adrianople was captured again in 923 and in 924 a Bulgar army laid siege to Constantinople. The situation in the Balkans improved only after Simeon's death in 927.Under the emperor Basil II (reigned 976–1025), the Bulgars, who had conquered much of the Balkans from the Byzantines since their arrival three hundred years previously, became the target of annual campaigns by the Byzantine army. The war was to drag on for nearly twenty years, but eventually at the Battle of Kleidon the Bulgars were completely defeated.The Bulgarian army was captured, and it is said that 99 out of every 100 men were blinded, with the remaining hundredth man left with one eye so as to lead his compatriots home. When tsar Samuil saw the broken remains of his once gallant army, he died of shock. In 1018 Bulgaria surrendered and became part of the empire. This stunning victory restored the Danube frontier, which had not been held since the days of the emperor Heraclius.The empire also gained a new ally at this time in the new Varangian state in Kiev, from which the empire received an important mercenary force, the famous Varangian Guard, in exchange for the marriage of Basil's sister Anna to Vladimir I of Kiev. During this period the Byzantine princess Theophanu, wife of the Holy Roman Emperor Otto II, served as regent of the Holy Roman Empire, paving the way for the westward spread of Byzantine culture.