In Eastern Europe, Byzantium revived its fortunes under Emperor Basil I (r. 867–886) and his successors Leo VI (r. 886–912) and Constantine VII (r. 913–959), members of the Macedonian dynasty. Commerce revived and the emperors oversaw the extension of a uniform administration to all the provinces. The military was reorganised, which allowed the emperors John I (r. 969–976) and Basil II (r. 976–1025) to expand the frontiers of the empire on all fronts. The imperial court was the centre of a revival of classical learning, a process known as the Macedonian Renaissance. Writers such as John Geometres (fl. early 10th century) composed new hymns, poems, and other works. Missionary efforts by both eastern and western clergy resulted in the conversion of the Moravians, Bulgars, Bohemians, Poles, Magyars, and Slavic inhabitants of the Kievan Rus'. These conversions contributed to the founding of political states in the lands of those peoples—the states of Moravia, Bulgaria, Bohemia, Poland, Hungary, and the Kievan Rus'. Bulgaria, which was founded around 680, at its height reached from Budapest to the Black Sea and from the Dnieper River in modern Ukraine to the Adriatic Sea. By 1018, the last Bulgarian nobles had surrendered to the Byzantine Empire.