Avars (known as Obri in Rus’ chronicles and Abaroi or Varchonitai in Byzantine sources). A large union of Turkic tribes. The Avars appeared in the steppes west of the Caspian Sea in the middle of the 6th century AD. After moving westward through the territories of today's Ukraine, they stopped for a time in the region north of the Black Sea. Here they persuaded the Alans and Ugrians to join their alliance. In the 560s on their way to the middle Danube River the Avars and their allies invaded the territory of the Antes. The Avars conquered and brought into their alliance a number of Slavic tribes. At the end of the 560s they established a khaganate on the middle Danube with a capital in Pannonia. From there the Avars made successful raids on the Slavs, Franks, Lombards, and Byzantium. As a result they controlled the territories from the Elbe River to Transcaucasia and from the Don River to the Adriatic Sea. The empire, however, lacked any organic political or economic unity, and when the Avars suffered a crushing defeat at Constantinople in 626, a series of revolts began among the subjugated tribes. The most important uprising—the uprising of the western Slavs—was led by Samo, and resulted in the founding of a Slavic state on the territory of present-day Czech Republic and Slovakia. The rise of the Bulgarian Kingdom in 680 and the victory of Charlemagne in 797 put an end to the Avar empire.