Oleg of Novgorod

Oleg succeeded his kinsman Rurik as prince of Novgorod, then pushed south along the Dnieper, subduing East Slavic tribes and making Kiev the center of his rule. He launched a successful attack on Constantinople, projecting Rus' power to Byzantium's gates. He died in 912 and was succeeded by Rurik's son Igor. The Primary Chronicle's timeline has drawn fire: the Schechter Letter mentions a khagan named Helgu active in the 940s under Romanus I, and historians still argue over whether Oleg was kin, regent, or rival to the Rurikid line.