114 CHRISTIAN GREECE AND LIVING GREEK. In 956 Olga, a Russian princess, came to Con- stantinople, where she was baptized. By her Christianity was introduced into Russia. From that time the Russians were generally friendly to the empire. The Bulgars, originally a Turkish tribe but who at present speak a Slavonic dialect, moved forward from the Volga to the Danube, invaded Thracia in 559 and menaced Constantinople. The city was saved by Belisarius. Thenceforth they were a source of continued trouble to the empire. The humanizing influence of Chris- tianity seemed to have mitigated the savagery of the Bulgars, when toward the close of the tenth century a war broke out which was fiercer than ever. After a bloody struggle lasting thirty years Basil 11. , the Bulgar slayer, completely shattered their power in 10 18, and Bulgaria was made a Byzantine province. One hundred and seventy years later they again rose in rebellion, after they had acknowledged the religious su- premacy of the Pope. Nevertheless while the Latin dynasty was reigning in Constantinople, John, Krai of the Bulgarians, fought on the Greek side against the Franks. The Magyars or Hungarians, another Turkish tribe, filled Europe with alarm until their power
