The Bulgarian Empire (Bulgarian: Българско царство, Balgarsko tsarstvo [ˈbəlɡɐrskʊ ˈt͡sarstvʊ]) existed in two distinct periods: between the seventh and eleventh centuries, and again between the twelfth and fourteenth centuries.
The First Bulgarian Empire was the first country of the modern Bulgarian people located in Southeastern Europe. Since its foundation it occupied a large part of the Balkan Peninsula and struggled with the Byzantine Empire for control of the region. Founded as a crude form of a confederacy between Bulgars, Slavs and Thracians in 681 on the two banks of the Danube river, it became the first Slavic country and is the oldest state still in existence in Europe. In 802-805 it destroyed the Avar Khanate and expanded its territory twice covering the whole area of what is now Romania. In the 9th and the beginning of the 10th century in the course of the Byzantine–Bulgarian wars the Bulgarians took control of most of the Balkans. However, in the mid 10th century the Empire suffered disastrous invasions of Magyars, Pechenegs and wars with Kievan Rus' and after a 50-year struggle it was destroyed by the Byzantines in 1018.
After the Christianization of Bulgaria the country became a major centre of culture and learning. Literature flourished in the Preslav and Ohrid Literary Schools. The Bulgarian scholar Clement of Ohrid ([840-916), who was a student of Saints Cyril and Methodius, invented the Cyrillic alphabet which carries the name of one of his teachers. Old Bulgarian became the lingua franca of much of Eastern Europe and it came to be known as Old Church Slavonic. The beauty and wealth of the capital Preslav was compared by some contemporaries with Constantinople. In the 10th century in Bulgaria emerged one of the major heretic movements in Medieval Europe, the Bogomils.
The Second Bulgarian Empire was established in 1185 as a result of the Uprising of Asen and Peter. 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 Epirus and made Bulgaria a regional power again. During his reign, Bulgaria spread from the Adriatic to the Black Sea and the economy flourished. In the late 13th century, however, the Empire declined under constant invasions by Mongols, Byzantines, Hungarians, and Serbs, as well as internal unrest and revolts. The 14th century saw a temporary recovery and stability, but also the peak of Balkan feudalism as central authorities gradually lost power in many regions. Bulgaria was divided into three parts on the eve of the Ottoman invasion.
Despite strong Byzantine influence, Bulgarian artists and architects created their own distinctive style. In the 14th century, during the period known as the Second Golden Age of Bulgarian culture, literature and art 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 for contemporary Bulgarians. After the Ottoman conquest, many Bulgarian clerics and scholars emigrated to Serbia, Wallachia, Moldavia, and Russian principalities, where they introduced Bulgarian culture, books, and hesychastic ideas.