Sviatoslav I of Kiev

Sviatoslav I or Svyatoslav I Igorevich (Old East Slavic: Свѧтославъ Игорєвичь, romanised: Svętoslavŭ Igorevičǐ; Old Norse: Sveinald; c. 943 – 972) was Prince of Kiev from 945 until his death in 972. He is known for his persistent campaigns in the east and south, which precipitated the collapse of two great powers in Eastern Europe, Khazaria and the First Bulgarian Empire. He conquered numerous East Slavic tribes, defeated the Alans and attacked the Volga Bulgars, and at times was allied with the Pechenegs and Magyars (Hungarians).

Following the death of his father Igor in 945, Sviatoslav's mother Olga reigned as regent in Kiev until 962. His decade-long reign over the Kievan Rus' was marked by rapid expansion into the Volga River valley, the Pontic steppe, and the Balkans, leading him to carve out for himself the largest state in Europe. In 969, he moved his seat to Pereyaslavets on the Danube. In 970, he appointed his sons Yaropolk and Oleg as subordinate princes of Kiev and Drelinia, while he appointed Vladimir, his son by his housekeeper and servant Malusha, as the prince of Novgorod.

In contrast with his mother's conversion to Christianity, Sviatoslav remained a staunch pagan all of his life. Due to his abrupt death in an ambush, his conquests, for the most part, were not consolidated into a functioning empire, while his failure to establish a stable succession led to a fratricidal feud among his three sons, resulting in the deaths of Yaropolk and Oleg, while Vladimir emerged as the sole ruler.