Russkaya Pravda
defeated Sviatopolk and became the Grand Prince of Kiev in 1019. Under Yaroslav the codification of legal customs and princely enactments began, and this work served as the basis for a law code called the "Russkaya Pravda" ("Rus Truth [Law]"). During Yaroslav's lengthy reign, Kievan Rus' reached the zenith of its cultural flowering and military power.