In 632,
Khan Kubrat united the
Bulgars into the state of
Old Great Bulgaria along the coasts of the
Black Sea and
Caspian Sea. After his death in the 660s his sons divided his kingdom amongst themselves.
Batbayan, the eldest son, inherited the throne in
Poltava but was defeated by and submitted to the rule of his ambitious relative Cozarig (
Kotrag) who had undermined the state's unity by leading his Don-Volga "Kutrigs" in expansion campaigns extending his empire to the north where
Volga Bulgaria would eventually form. The third son
Asparuh marched westward and settled in the Ongal area on the eastern banks of the
Danube. Eventually the
Avars fought back and after Asparuh consolidated his rule they launched an attack against the
Byzantine lands to the south. During that time the Byzantine Empire was at war with the
Arabs who had recently
besieged the capital
Constantinople. However, in 680 the
Byzantines defeated the Arabs and concluded a peace treaty. After this success the emperor
Constantine IV was free to move against the
Bulgars and led an army against Asparuh. In the meantime the Bulgar leader made an alliance with the
Seven Slavic tribes for mutual protection against the Byzantines and formed a federation. ==Battle==