Slavonia was not only christened but regenerated at this period, and infused into it were the new elements of martial order, discipline, and the habit of implicit obedience to a chosen or hereditary chief; and as Rurik's brothers soon conveniently died, their territory also passed to him, and he assumed the title of Grand Prince.
Upon the death of Rurik in 879, his younger brother Oleg succeeded him as regent during the minority of his son Igor; and when two more Varangian brothers--Askold and Dir--in the same manner--except that they were not invited--took possession of Kief on the Dnieper and set up a rival principality in the South with ambitious designs upon Byzantium, Oleg promptly had them assassinated, added their territory to the dominion of Igor, and removed the capital from Novgorod to Kief--saying, "Let Kief be the mother of Russian cities!" Then after selecting a wife named Olga for the young Igor, he turned his attention toward Byzantium, the powerful magnet about which Russian policy was going to revolve for many centuries.
So invincible and so wise was this Oleg that he was believed to be a sorcerer.

When the Greek emperor blockaded the passage of the Bosphorus in 907, he placed his two thousand boats (!) upon wheels, and let the sails carry them overland to the gates of Constantinople.

The Russian poet Pushkin has made this the subject of a poem which tells how Oleg, after exacting tribute from the frightened Emperor Leo VI., in true Norse fashion, hung his shield upon the golden gates as a parting insult.
Again and again were the Greeks compelled to pay for immunity from these invasions of the Varangian princes.

After the death of Oleg, Igor reigned, and in 941 led another expedition against Constantinople which we are told was driven back by "Greek-fire." Then enlisting the aid of the Pechenegs, a ferocious Tatar tribe, he returned with such fury, and inflicted such atrocities, that the Greek Emperor begged for mercy and offered to pay any price to be left alone.

The invaders said: "If Caesar speaks thus, what more do we want than to have gold and silver and silks without fighting." A treaty of peace was signed (945), the Russians swearing by their god Perun, and the Greeks by the Gospels; and the victorious Igor turned his face toward Kief.