Annales regni Francorum
Another century and a half passed before the Avars were finally defeated between 792 and 796 by Charlemagne, ruler of the Frankish Empire. In short time a series of Slavic principalities emerged in the regions on the Middle Danube. Among these polities, the Moravian principality showed up for the first time in 822 when the Moravians, according to the "Royal Frankish Annals", brought tribute to Charlemagne's son, Emperor Louis the Pious.