Britannica:The Bulgars…. originated as a Turkic tribe ... ENCYCLOPAEDIA BRITANNICA Bulgar also called BULGARIAN, member of a people known in eastern European history during the Middle Ages. One branch of this people was an ancestor of the modern Bulgarians. The Bulgars probably originated as a Turkic tribe of Central Asia and arrived in the European steppe west of the Volga River with the Huns about AD 370; retreating with the Huns, they resettled about 460 in an arc of country north and east of the Sea of Azov. Hired by the Byzantines in 480 to fight against the Ostrogoths, the Bulgars subsequently became attracted by the wealth of the Byzantine Empire. In the 6th century the Bulgars continually attacked the Danubian provinces of the Byzantine Empire until, in the 560s, they were themselves threatened by the Avars, who were then advancing from Asia into central Europe. The Avars destroyed one Bulgar tribe, but the rest saved themselves by submitting, for two decades, to another horde of Turkic newcomers, most of whom then retreated back into Asia. Unified under a single ruler, Kurt, or Kubrat (reigned c. 605-c. 642), the Bulgars constituted a powerful khanate known to the Byzantines as Great Bulgaria, with the Kuban River as its southern frontier. After Kurt's death his five sons split the people into five hordes. One of these five, remaining on the coast of the Sea of Azov, was absorbed into the new empire of the Khazars; another migrated to central Europe and was merged with the Avars; and another disappeared into service under the Lombards in Italy. Two of the five hordes, however, had longer futures. Kurt's son Bezmer, or Bat-Bayan, avoided the Khazars by leading his horde far to the north, where it eventually occupied an ill-defined country around the confluence of the Volga and Kama rivers. Subdivided there into three groups (probably through mergers with indigenous peoples or with other immigrants), the horde maintained itself in prosperity for some 600 years. These Volga Bulgars formed not so much a state as a seminomadic confederation, but they had two cities, Bulgar and Suvar, which profited as transshipment points in the trade between the fur-selling Ugrians and Russians of the far north and the southern civilizations--Byzantium, the Muslim Caliphate of Baghdad, and Turkistan. The Volga Bulgars were converted to Islam about 922. In 1237 they were made subject to the Mongol Golden Horde, and, though the city of Bulgar flourished for a long time afterward, the people gradually lost their identity and were mingled with the Russians. The fifth product of the breakup of Great Bulgaria was the horde that Kurt's son Asparukh led westward across the Dniester River and then southward across the Danube. There, on the plain between the Danube and the Balkan Mountains, they established the kernel of the so-called first Bulgarian empire--the state from which the modern nation of Bulgaria derives its name. In the 7th century the Danubian region was nominally controlled by the Byzantine Empire, and it was inhabited by Vlachs (ancestors of the modern Romanians) and also very largely by recently arrived Slavs. The conquering Bulgars were soon permeated by Vlach and, even more thoroughly, by Slavic elements. At the same time, their conquests were carrying them deeper into the ambit of Byzantine Christianity. Territorial expansion into Serbia and Macedonia under Krum (khan 803-814) and under Pressian (836-852) was followed by the conversion of the Bulgars to Christianity under Boris I. The new church's liturgy was in the Slavic language as spoken in the Bulgars' Macedonian possessions, and this language, now known as Old Church Slavonic