The troubled years after Justinian's death also witnessed the beginning of the Slavic [12] settlements in southeastern Europe. The Slavs belonged to the Indo-European race, but had not progressed in civilization as far as the Germans. Their cradle land seems to have been in western Russia, whence they slowly spread to the Baltic, the Elbe, and the Danube. We have already mentioned the campaigns which Charlemagne and Henry the Fowler waged against them. [13] The emperors at Constantinople were less successful in resisting that branch of the Slavs which tried to occupy the Balkan peninsula. After crossing the Danube, the Slavs pressed on farther and farther, until they reached the southern extremity of ancient Greece. They avoided the cities, but formed peasant communities in the open country, where they readily mingled with the inhabitants. Their descendants have remained in the Balkan peninsula to this day. The inhabitants of modern Serbia [14] are Slavs, and even in the Greeks there is a considerable strain of Slavic blood. BULGARIANS The Bulgarians, a people akin to the Huns and Avars, made their appearance south of the lower Danube in the seventh century. For more than three hundred years these barbarians, brutal, fierce, and cruel, were a menace to the empire. At one time they threatened Constantinople and even killed a Roman emperor, whose skull was converted into a drinking cup to grace their feasts. The Bulgarians settled in the region which now bears their name and gradually adopted the speech and customs of the Slavs. Modern Bulgaria is essentially a Slavic state. RUSSIANS The empire was attacked in southeastern Europe by still other barbarians, among whom were the Russians. This Slavic people, led by chieftains from Sweden, descended the Dnieper and Dniester rivers and, crossing the Black Sea, appeared before the walls of Constantinople. Already, in the tenth century, that city formed the goal of Russian ambitions. The invaders are said to have made four attempts to plunder its treasures. Though unsuccessful, they compelled the emperors from time to time to pay them tribute. WORK OF THE EMPIRE IN EUROPE Christianity reached the invaders of the Balkan peninsula from Constantinople. The Serbians, Bulgarians, and Russians were converted in the ninth and tenth centuries. With Christianity they received the use of letters and some knowledge of Roman law and methods of government. Constantinople was to them, henceforth, such a center of religion and culture as Rome was to the Germans. By becoming the teacher of the vast Slavic peoples of the Balkan peninsula and European Russia, the empire performed another important service to civilization. 118. BYZANTINE CIVILIZATION STRENGTH AND WEALTH OF THE EMPIRE