situation held great risk for the weakened Bulgarian state. War broke out with the Byzantine Empire between 855 and 856. The Byzantines wanted to regain control over some fortresses on the Diagonal Road (Via Diagonalis or Via Militaris) that went from Constantinople, through Philippopolis (Plovdiv), to Naissus (Niš) and Singidunum (Belgrade). The Byzantine Empire was victorious and reconquered a number of cities, with Philippopolis being among them. In 861 Khan Boris concluded an alliance with East Frankish King Louis the German, all while informing him that he would like to accept Christianity according to western rite. This renewed alliance threatened Great Moravia, which sought help from Byzantium (862–863). This was at the same time when a Byzantine mission to Great Moravia was taking place. Cyril and his brother Methodius intended to draw Great Moravia closer to Constantinople and strengthen the Byzantine influence there. Khan Boris was more interested in the first Slavonic alphabet Cyril and Methodius had created. Bulgaria wanted to implement the Slavonic alphabet as well as a means to stop the cultural influence of the Byzantine Empire. In the last months of 863 the Byzantines attacked Bulgaria again, probably after having been informed by their Moravian allies that Boris told the German king he was willing to accept Christianity and Byzantium had to forestall him from taking up Christianity from Rome. A Rome-dependent Bulgaria in the hinterland of Constantinople was a threat to the Byzantine Empire's immediate interests. Aligning with the East Before any actual military engagements took place, Khan Boris was forced to sue for peace due to being unprepared for war because of Bulgaria being badly affected by crop failure and earthquakes that year, which Boris may have taken for a sign to convert according to the eastern rite. Negotiations were set up and Boris promised to convert to Eastern Orthodox Christianity along with his people, requesting missionaries to come to Bulgaria and begin the process. The two sides concluded a "deep peace" for a 30-year period. In exchange for Bulgaria's conversion, the Byzantines returned previously conquered lands. In the late autumn of 864, a mission from the Patriarch of Constantinople Photios arrived at the Bulgarian capital Pliska and converted the Khan, his family and high-ranking dignitaries. Boris was given the Christian name Michael (after then Byzantine Emperor Michael III) and, according to most scholars, changed his title to the Slavic equivalent of King (Knyaz). After