Oleg was the ruler of Drelinia, a region which is today in the western Ukraine. The Drevlians ( Деревляни, Derevliany in Ukrainian; Древляне, Drevlyane in Russian) were a Tribe Ukraine (Україна Ukrayina, /ukrɑˈjinɑ/ is a country in Eastern Europe.
He was the son of Sviatoslav I of Kiev. Sviatoslav I of Kiev ( Old East Slavic: С~тославъ (Свąтославъ Игорєвичь ( Sventoslavŭ Igorevichǐ) Russian: ru Святослав Sviatoslav split up his domains, and gave Drevlinia to Oleg. Oleg and his brother Yaropolk went to war after their father's death. Yaropolk I Svyatoslavich (c 958- 960 - 11 June ? 980 ( East Slavic: Ярополк I Святославич sometimes transliterated as Iaropolk This war eventually resulted in Oleg's defeat and the reunification of his lands with Kiev.