changed his title after his conversion to Christianity. According to them, before the baptism he had the title Khan or Kanasubigi, and after that Knyaz. Reign Central Europe in the 9th century The early 9th century marked the beginning of a fierce rivalry between the Greek East and Latin West, which would ultimately lead to the schism between the Orthodox Church in Constantinople and the Catholic Church in Rome. As early as 781, the Empress Irene began to seek a closer relationship with the Carolingian dynasty and the Papacy. She negotiated a marriage between her son, Constantine, and Rotrude, a daughter of Charlemagne by his third wife Hildegard. Irene went as far as to send an official to instruct the Frankish princess in Greek; however, Irene herself broke off the engagement in 787, against her son's wishes. When the Second Council of Nicaea of 787 reintroduced the veneration of icons under Empress Irene, the result was not recognized by Charlemagne since no Frankish emissaries had been invited even though Charlemagne was by then ruling more than three provinces of the old Roman empire. While this improved relations with the Papacy, it did not prevent the outbreak of a war with the Franks, who took over Istria and Benevento in 788. When Charlemagne was proclaimed Emperor of the Holy Roman Empire by Leo III, the Pope was effectively nullifying the legitimacy of Irene. He certainly desired to increase the influence of the papacy and to honour his protector Charlemagne. Irene, like many of her predecessors since Justinian I, was too weak to protect Rome and its much reduced citizenry and the city was not being ruled by any emperor. Thus, Charlemagne's assumption of the imperial title was not seen as an usurpation in the eyes of the Franks or Italians. It was, however, seen as such in Byzantium, but protests by Irene and her successor Nicephorus I had no great effect. Mojmír I managed to unite some Slavic princes and established Great Moravia in 833. His successor, Rastislav, also fought against the Germans. Both states tried to maintain good relations with Bulgaria on account of its considerable military power. 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,