Sviatoslav I (died 972) achieved the first major expansion of Kievan Rus' territorial control, fighting a war of conquest against the Khazars.Vladimir the Great (980–1015) introduced Christianity with his own baptism and, by decree, extended it to all inhabitants of Kiev and beyond.
Ahmad ibn Fadlan, an Arab traveler during the 10th century, provided one of the earliest written descriptions of the Rus': "They are as tall as a date palm, blond and ruddy, so that they do not need to wear a tunic nor a cloak; rather the men among them wear garments that only cover half of his body and leaves one of his hands free." but explains the name as a Greek term referring to their physical traits ("A certain people made up of a part of the Norse, whom the Greeks call [...] the Russi on account of their physical features, we designate as Norsemen because of the location of their origin.").
Trade from the Baltic also moved south on a network of rivers and short portages along the Dnieper known as the "route from the Varangians to the Greeks," continuing to the Black Sea and on to Constantinople.
Kiev was a central outpost along the Dnieper route and a hub with the east-west overland trade route between the Khazars and the Germanic lands of Central Europe.
trading and frequently allying with the Byzantine Empire against Persians and Arabs.
In the late 8th century, the collapse of the Göktürk Khaganate led the Magyars and the Pechenegs, Ugric and Turkic peoples from Central Asia, to migrate west into the steppe region, The Byzantines established the Theme of Cherson, formally known as Klimata, in the Crimea in the 830s to defend against raids by the Rus' and to protect vital grain shipments supplying Constantinople.
In 862, the Finnic and Slavic tribes in the area of Novgorod rebelled against the Varangians, driving them "back beyond the sea and, refusing them further tribute, set out to govern themselves." The tribes had no laws, however, and soon began to make war with one another, prompting them to invite the Varangians back to rule them and bring peace to the region: They said to themselves, "Let us seek a prince who may rule over us, and judge us according to the Law." They accordingly went overseas to the Varangian Rus'. The Chuds, the Slavs, the Krivichs and the Ves then said to the Rus', "Our land is great and rich, but there is no order in it. They thus selected three brothers with their kinfolk, who took with them all the Rus' and migrated.