Khagan Kotrag(Chuvash: Кăтра Паттăр, Kătra Pattăr) was the son of Kubrat of the Dulo clan who inherited the leadership of the Kazarigs. Khagan Kotrag simply means leader of the Kotrags and may refer to at least two or more people such as Khalga and Kaban who may or may not in fact have descended from Khagan Kubrat. Following the death of his father, he dethroned his brother Batbayan in old Great Bulgaria and began to extend the influence of his Kazarig Bulgars up the Volga river. He is remembered as the founder of Volga Bulgaria. His successors reached the lands of modern Tatarstan and established a state during the 7th to 9th centuries and recognised Islam as the official religion in 922 AD during the visit of Baghdad khalifat ambassador Ibn Fazlan and remained independent up until the 13th century, when it was conquered by the Batu-khan hordes of Mongolic and Turkic people widely known as Mongol-Tatars. The country's capital was called "Bulgar" or "Great Bulgar".