What events resulted in the unification of the lands of the Eastern Slavs?

The unification of the lands of the Eastern Slavs occurred as a result of the conquest of Kiev by Oleg. It is believed that the beginning of statehood among the Eastern Slavs is the arrival of Oleg to Russia. He ruled in Novgorod, but in order to create a unified state, he went with his squad to Kiev. After the victory over the capital of the Polyans, the prince united the two cities. He also subdued the tribes of the Radimichi, Drevlyans, and Northerners. Presumably for this purpose, Oleg killed Askold and Dir, who ruled in Kiev before him. 882 can be considered the beginning of statehood.