Alexander Vasiliev and George Vernadsky, among others, argue that Sarkel was built to defend a vital portage between the Don and the Volga from the Rus' Khaganate.
Sarkel |
Constantine Porphyrogenitus wrote in his work On Administering the Empire that the Khagan and the Bek of the Khazars asked the Emperor Teophilos to have the fortress of Sarkel built for them.