Igor returned to Kiev keen for revenge. He assembled a large force of warriors from among neighboring Slavs and Pecheneg allies, and sent for reinforcements of Varangians from "beyond the sea." In 944 the Rus' force advanced again on the Greeks, by land and sea, and a Byzantine force from Cherson responded. The Emperor sent gifts and offered tribute in lieu of war, and the Rus' accepted. Envoys were sent between the Rus', the Byzantines, and the Bulgarians in 945, and a peace treaty was completed. The agreement again focused on trade, but this time with terms less favorable to the Rus', including stringent regulations on the conduct of Rus' merchants in Cherson and Constantinople and specific punishments for violations of the law. The Byzantines may have been motivated to enter the treaty out of concern of a prolonged alliance of the Rus', Pechenegs, and Bulgarians against them, though the more favorable terms further suggest a shift in power.
Try to answer this question if possible (otherwise reply "unanswerable"): What year did the Rus defeat the Byzantines the the Bulgarians?
unanswerable