and Emperor Simeon the Great, when its early Christianization in 864 allowed it to develop into the cultural and literary center of Slavic Europe, as well as one of the largest states in Europe, thus the period is considered the Golden Age of medieval Bulgarian culture. Major events included the development of the Cyrillic script at the Preslav Literary School, declared official in 893, and the establishment of the liturgy in Old Bulgarian, also called Old Church Slavonic. In 971, the capital city of Preslav was occupied by the Kievan Rus' and the Eastern Roman Empire consequently. In 1018, the First Bulgarian Empire ended and Bulgaria became a province of the Byzantine Empire, the Theme of Bulgaria (1018-1185). Second Bulgarian Empire The medieval Bulgarian state was restored as the Second Bulgarian Empire after a successful uprising of two nobles from Tarnovo, Asen and Peter, in 1185, and existed until it was conquered during the Ottoman invasion of the Balkans in the late 14th century, with the date of its subjugation usually given as 1396, although some fringe views place it at 1422. Until 1256, the Second Bulgarian Empire was the dominant power in the Balkans, defeating the Byzantine Empire in several major battles. In 1205, Emperor Kaloyan defeated the newly established Latin Empire in the Battle of Adrianople. His nephew Ivan Asen II defeated the Despotate of Epiros and made Bulgaria a regional power again. During his reign, Bulgaria spread from the Adriatic to the Black Sea and the economy flourished. Under Ivan Asen II in the first half of the 13th century the country gradually recovered much of its former power, though this did not last long due to internal problems and foreign invasions. Bulgarian artists and architects created their own distinctive style. Until the 14th century, during the period known as the Second Golden Age of Bulgarian culture, literature, art and architecture flourished. The capital city Tarnovo, which was considered a "New Constantinople", became the country's main cultural hub and the centre of the Eastern Orthodox world. The Empire became tributary to the Golden Horde, a successor state of the Mongol Empire in the 13th to 14th centuries. After the death of Emperor Ivan Alexander in 1371 Bulgaria was split into three countries and in the following decades fell under the domination of the Ottomans. In 1393 after siege Tarnovo was conquered by the Ottoman Empire and in