known as Yaroslav the Wise
born 980
died Feb. 2, 1054
Grand prince of Kiev (1019–54).
A son of Vladimir I , he defeated his brother Svyatopolk the Accursed to become ruler of Kiev. He consolidated the state through administrative reforms and military campaigns, codified laws, and promoted the spread of Christianity. He also built many fortifications and churches in the Byzantine style, including the Cathedral of St. Sophia. Yaroslav regained Galicia from the Poles and expanded Kievan possessions in the Baltic region, but his military campaign against Constantinople was a failure (1043).