The Vikings indeed had long-established and profitable trade relationships with the inhabitants of the lands to the east of Scandinavia. However, as one might anticipate, the Vikings' interactions with these people weren't solely peaceful and often included military activities.
Vikings comprised the elite warriors within the army that fought for and safeguarded the Byzantine emperor in Constantinople (modern-day Istanbul, Turkey). These Viking warriors were known as the "Varangians," and while they served as mercenaries, they gained a reputation for their unwavering loyalty.
During the ninth century, Vikings launched invasions into and subsequently conquered the region we now know as Russia. Their conquest led to the establishment of the Rurikid dynasty, which ruled over Russia until the sixteenth century. Additionally, the Vikings bestowed upon Russia its name, as the local Slavic inhabitants began to refer to them as the "Rus."
