Kievan Rus, which was considered the first Russian state, was formed in a land characterized by forbidding forests and an absence of natural barriers to the menace of hostile invasion, the summer's heat or the winter's cold. Although the territory had long been inhabited by various tribal groups, the Slavic tribes dominated the area after about the 6th century. This was also the time when the common Slavic language began to evolve the subgroups, West, South and East Slavic, to which Ukrainian belongs. Over time, the Slavs, who were northern agriculturalists originally from the Carpathian Mountains and the Vistula valley, engaged in trade with Arab and Byzantine merchants.
As trade routes developed, the Byzantine Varangians, or followers of a chieftain, gained the leadership of the local Slavic tribes and through their leadership, the powerful Kievan State was formed. In the early 9th century, the Slavic tribes were attacked from the northwest. The Scandinavian Vikings, who were simultaneously attacking Scotland, Iceland, Ireland, England, Germany, France and Spain, sent small bands of men into northern Russia to prey upon the communities of the Balts, Finns, and Slavs, and then return with their booty. To protect their robberies with law and order, the Varangians established fortified posts along their attack routes and gradually settled down as a ruling Scandinavian minority of armed merchants among a subject peasantry.
By the middle of the 9th century, the Varangians governed Novgorod (or new fort) and had extended their rule as far south as Kiev. The routes and settlements they controlled were loosely bound into a commercial and political empire called Rus, a term of much disputed derivation. The great rivers that traversed the land connected the Baltic and Black Seas, and invited a southward expansion of Varangian trade and power. Soon these fearless merchant-warriors were selling their goods or services in Constantinople itself. Although the Varangians had a strong impact on the political organization of this area, their cultural influence was minimal and they rapidly assumed the East Slavic language and culture.
The political structure of Kievan Rus' was a blending of monarchic, aristocratic and democratic elements. Under the authority of the grand prince of Kiev were territorial princes, the boyar councils (duma) and the town assemblies. The princes were expected to provide justice, order and protection for their subjects and governors were appointed to rule distant areas. The prince relied on the duma for advice and support. The town assembly, which had its roots in early tribal councils, was called when the need to express public opinion arose. In the assemblies, topics of discussion included war, royal succession, appointments to office and the negotiation of treaties; however, they could only comment on policy and did not have the power to form their own laws.
The first Kievan prince, Oleh or Helgi in Scandinavian, was established in 882, and his dynasty known as the Riurikids. As the leader of the Polianian tribe, he soon extended his authority over the other tribes. Under Vladimir and his son Iaroslav, in the 11th century Kievan Rus' reached the height of power, stability and prosperity. Vladimir, the fifth grand Duke of Kiev, married the sister of the Emperor Basil II and thus, until the Soviet era, Russia was a daughter of Byzantium in religion, alphabet, coinage and art. In addition to expanding and modernizing his realm, Vladimir brought Orthodox Christianity to his people in 988. Greek priests explained to Vladimir the divine origin and right of kings, and the usefulness of this doctrine in promoting social order and monarchical stability. Before Vladimir's conversion, Russian religion was based on a number of gods representing the forces of nature and on the worship of ancestors. The acceptance of Christianity had an immense impact on the culture of Kievan Rus' because it increased the Byzantine and Greek influence on the territory. The Byzantine influence is revealed in the architecture, the system of writing, and crafts from the period. For example, the famous cathedral St. Sophia was built in Kiev in 1037. However, the 12th century was period was a time of princely feuds, economic stagnation and nomadic invasions. In the 13th century, the disintegrating Kievan Rus' was conquered by the Mongols and the capture of Kiev in 1240 signaled the end of the Riurikid dynasty.