Kubrat was endorsed by Khan Sibir as the first king of Onogur, the 2nd Avar dynasty. Under his and his son Bayan's rule, Avaria grew to stretch from the Danube to the Volga rivers. In 619 CE he arrived as hostage in Constantinople and was soon baptized. His maternal uncle Organa (also Organ or Ornag) acted as regent over his tribe the Unogundur until he was old enough to rule. Kubrat established peace with Byzantium, due to his respect for Byzantine culture. He was buried near Poltava (from Balt-Avar, meaning 'Chief of Avars').