<P> Led by a Varangian dynasty, the Kievan Rus' controlled the routes connecting Northern Europe to Byzantium and to the Orient (for example: the Volga trade route). The Kievan state began with the rule (882--912) of Prince Oleg, who extended his control from Novgorod southwards along the Dnieper river valley in order to protect trade from Khazar incursions from the east and moved his capital to the more strategic Kiev . Sviatoslav I (died 972) achieved the first major expansion of Kievan Rus' territorial control, fighting a war of conquest against the Khazar Empire and inflicting a serious blow on Bulgaria . A Rus' attack (967 or 968), instigated by the Byzantines, led to the collapse of the Bulgarian state and the occupation of the east of the country by the Rus' . An ensuing direct military confrontation between the Rus' and Byzantium (970 - 971) ended with a Byzantine victory (971). The Rus' withdrew and the Byzantine Empire incorporated eastern Bulgaria . Both before and after their conversion to Christianity (conventionally dated 988 under Vladimir I of Kiev--known as Vladimir the Great), the Rus' also embarked on predatory military campaigns against the Byzantine Empire, some of which resulted in trade treaties . The importance of Russo - Byzantine relations to Constantinople was highlighted by the fact that Vladimir I of Kiev, son of Svyatoslav I, became the only foreigner to marry (989) a Byzantine princess of the Macedonian dynasty (which ruled the Eastern Roman Empire from 867 to 1056), a singular honour sought in vain by many other rulers . </P> <P> With the end of the Western Roman Empire and with urban centres in decline, literacy and learning decreased in the West . This continued a pattern that had been underway since the 3rd century . Much learning under the Roman Empire was in Greek, and with the re-emergence of the wall between east and west, little eastern learning continued in the west . Much of the Greek literary corpus remained in Greek, and few in the west could speak or read Greek . Due to the demographic displacement that accompanied the end of the western Roman Empire, by this point most western Europeans were descendants of non-literate barbarians rather than literate Romans . In this sense, education wasn't lost so much as it had yet to be acquired . </P> <P> Education did ultimately continue, and was centred in the monasteries and cathedrals . A "Renaissance" of classical education would appear in Carolingian Empire in the 8th century . In the Eastern Roman Empire (Byzantium), learning (in the sense of formal education involving literature) was maintained at a higher level than in the West . The classical education system, which would persist for hundreds of years, emphasized grammar, Latin, Greek, and rhetoric . Pupils read and reread classic works and wrote essays imitating their style . By the 4th century, this education system was Christianized . In De Doctrina Christiana (started 396, completed 426), Augustine explained how classical education fits into the Christian worldview: Christianity is a religion of the book, so Christians must be literate . Tertullian was more skeptical of the value of classical learning, asking "What indeed has Athens to do with Jerusalem?" </P> <P> De-urbanization reduced the scope of education, and by the 6th century teaching and learning moved to monastic and cathedral schools, with the study of biblical texts at the centre of education . Education of the laity continued with little interruption in Italy, Spain, and the southern part of Gaul, where Roman influences were more long - lasting . In the 7th century, however, learning expanded in Ireland and the Celtic lands, where Latin was a foreign language and Latin texts were eagerly studied and taught . </P>

What served as centers of learning in early medieval europe