Decline of the Carolingian Empire in the middle of the 9th century was taken advantage by the Slavic peoples who established the Empire of Great Moravia in today’s Bohemia, Silesia, Slovakia, southern Poland and northern Hungary. About the same time the territory of Great Moravia became a conflict area between East Francia and the Byzantine Empire. Great Moravian Prince, Rastislav (r. 846-870) turned to the Byzantine Emperor Michael III with an aim to loose himself of the Carolingian political as well as religious pressure. Thus Rastislav asked the Byzantine Emperor to send him teachers who would interpret Christianity in the Slavic vernacular. Missionaries Saints Cyril and Methodius arrived in Great Moravia in 864 but Svatopluk I (r. 871-894) who overthrown Rastislav with Carolingian support expelled the followers of Saints Cyril and Methodius.
The period after the Svatopluk’s death in 894 was marked by the internal struggles and constant warfare with East Francia which was taken advantage by the Hungarians who invaded and destroyed Great Moravia in the early 10th century.