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In his foreign policy, Yaroslav relied on the Scandinavian alliance and
attempted to weaken the Byzantine influence on Kiev. In 1030 he
reconquered from the Poles Red Rus, and concluded an alliance with king
Casimir I the Restorer, sealed by the latter's marriage to Yaroslav's
sister Maria. In another successful military raid the same year, he
founded Yuriev (after St George, or Yury, Yaroslav's patron saint) and
forced the surrounding province of Ugaunia to pay annual tribute.
One of many statues of Yaroslav holding the Ruskaya Pravda in his hand.
See another image here.In 1043 Yaroslav staged a naval raid against
Constantinople led by his son Vladimir and general Vyshata. Although the
Rus' navy was defeated, Yaroslav managed to conclude the war with a
favourable treaty and prestigious marriage of his son Vsevolod to the
emperor's daughter. It has been suggested that the peace was so
advantageous because the Kievans had succeeded in taking a key Byzantine
possession in Crimea, Chersones.
To defend his state from the Pechenegs and other nomadic tribes
threatening it from the south he constructed a line of forts, composed
of Yuriev, Boguslav, Kaniv, Korsun, and Pereyaslav. To celebrate his
decisive victory over the Pechenegs in 1036 (who thereupon never were a
threat to Kiev) he sponsored the construction of the Saint Sophia
Cathedral in 1037. Other celebrated monuments of his reign, such as the
Golden Gates of Kiev, have since perished.