Byzantine–Bulgarian wars
Military conflict connected to the Christian conversion of Boris

In 863 Boris made a decision to embrace Christianity, and he sought a mission from the Franks. The Byzantines could not countenance so close a neighbor as Bulgaria falling under Frankish religious control. Byzantium had recently gained a major victory over the Arabs and was free to field a considerable military force against Bulgaria. A fleet was sent into the Black Sea and an army dispatched to invade Bulgaria. As the bulk of Boris' army was campaigning against Moravia far to the northwest, he had little choice but to yield immediately. He broke off the Frankish alliance, allowed Greek clergy to enter Bulgaria, and was eventually baptized, with the Byzantine emperor Michael III as his sponsor; Boris took the additional name of Michael at his baptism. The Bulgarians were allowed to recover the debatable region of Zagora as a reward for their change of religious orientation.
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