Yaroslav, known as "the Wise", struggled for power with his brothers. A son of Vladimir the Great, he was vice-regent of Novgorod at the time of his father's death in 1015. Subsequently, his eldest surviving brother, Svyatopolk the Accursed, killed three of his other brothers and seized power in Kiev. Yaroslav, with the active support of the Novgorodians and the help of Viking mercenaries, defeated Svyatopolk and became the grand prince of Kiev in 1019. Although he first established his rule over Kiev in 1019, he did not have uncontested rule of all of Kievan Rus' until 1036. Like Vladimir, Yaroslav was eager to improve relations with the rest of Europe, especially the Byzantine Empire. Yaroslav's granddaughter, Eupraxia the daughter of his son Vsevolod I, Prince of Kiev, was married to Henry III, Holy Roman Emperor. Yaroslav also arranged marriages for his sister and three daughters to the kings of Poland, France, Hungary and Norway. Yaroslav promulgated the first East Slavic law code, Russkaya Pravda; built Saint Sophia Cathedral in Kiev and Saint Sophia Cathedral in Novgorod; patronized local clergy and monasticism; and is said to have founded a school system. Yaroslav's sons developed the great Kiev Pechersk Lavra (monastery), which functioned in Kievan Rus' as an ecclesiastical academy.