Boris I of Bulgaria
Military campaigns

Boris I was the son and successor of Presian I of Bulgaria. In 852 he sent emissaries to Eastern Francia to confirm the peace treaty of 845. At the time of his accession he threatened the Byzantines with an invasion, but his armies did not attack, and he received a small area in Strandzha to the southeast. The peace treaty was not signed, however, although both states exchanged temporary delegations. In 854 the Moravian Prince Rastislav persuaded Boris I to help him against East Francia. According to some sources, some Franks bribed the Bulgarian monarch to attack Louis the German. The Bulgarian-Slav campaign was a disaster, and Louis scored a great victory and invaded Bulgaria. At the same time the Croats waged a war against the Bulgarians. Both peoples had coexisted peacefully up to that time, suggesting that the Croats were paid by Louis to attack Bulgaria and distract Boris' attention from his alliance with Great Moravia. Kanasubigi Boris could not achieve any success, and both sides exchanged gifts and settled for peace. As a result of the military actions in 855, the peace between Bulgaria and Eastern Francia was restored, and Rastislav was forced to fight against Louis alone. In the meantime, a conflict between the Byzantines and Bulgarians had started in 855–856, and Boris, distracted by his conflict with Louis, lost Philippopolis (Plovdiv), the region of Zagora, and the ports around the Gulf of Burgas on the Black Sea to the Byzantine army led by Michael III and the caesar Bardas.
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