Simeon I of Bulgaria in the context of "Patriarchate"

The Byzantine–Bulgarian wars were a series of conflicts fought between the Byzantine Empire and the Bulgarian Empire which began after the Bulgars conquered parts of the Balkan peninsula after 680 AD. The Byzantine and First Bulgarian Empire continued to clash over the next century with varying success, until the Bulgarians, led by Krum, inflicted a series of crushing defeats on the Byzantines. After Krum died in 814, his son Omurtag negotiated a thirty-year peace treaty. Simeon I had multiple successful campaigns against the Byzantines during his rule from 893 to 927. His son Peter I negotiated another long-lasting peace treaty. His rule was followed by a period of decline of the Bulgarian state.

In 971 John I Tzimiskes, the Byzantine emperor, subjugated much of the weakening Bulgarian Empire by defeating Boris II and capturing Preslav, the Bulgarian capital. Samuel managed to stabilize the Bulgarian state with its center around the town of Prespa. Near the end of his rule, the Byzantines regained the upper hand, and under Basil II they won the Battle of Kleidion and completely conquered Bulgaria in 1018. There were rebellions against Byzantine rule from 1040 to 1041, and in the 1070s and the 1080s, but these failed. In 1185, however, Theodore Peter and Ivan Asen started a revolt, and the weakening Byzantine Empire, facing internal dynastic troubles of its own, was unable to quash the revolt.

Principality of Serbia (Modern Serbian: Кнежевина Србија / Kneževina Srbija; also known as Principality of Serbs, (Modern Serbian: Кнежевина Срба / Kneževina Srba; Latin: Principatum Serborum; Modern Greek: Πριγκιπάτο της Σερβίας) was one of the early medieval states of the Serbs, located in the western regions of Southeastern Europe. It existed from the 8th century up to c. 969–971 and was ruled by the Vlastimirović dynasty. Its first ruler known by name was Višeslav, who started ruling around 780, while by that time (starting from the years 680–681), the Bulgarian state had taken the lands to the east. Vlastimir resisted and defeated the Bulgarian army in a three-year-war (839–842), and the two powers lived in peace for some decades. Vlastimir's three sons succeeded in ruling Serbia together, although for a limited time; Serbia became a key part in the power struggle between the Byzantines and Bulgarians, predominantly allied with the Byzantines, which also resulted in major dynastic wars for a period of three decades. The principality was annexed in 924 by Simeon I and subjected to Bulgarian rule until 933 when Serbian prince Časlav was established as ruler of the Serbian land, becoming the most powerful ruler of the Vlastimirović dynasty.

An important process during this period was the Christianization of the Serbs, completed by the establishment of Christianity as state-religion in the second half of the 9th century. The principality was annexed by the Byzantines in c. 969–971 and ruled as the Catepanate of Ras. The main information of the history of the principality and Vlastimirović dynasty are recorded in the contemporary historical work De Administrando Imperio (written c. 948–949).

The Golden Age of Bulgaria is the period of the Bulgarian cultural prosperity during the reign of emperor Simeon I the Great (889—927). The term was coined by Spiridon Palauzov in the mid 19th century. During this period there was an increase of literature, writing, arts, architecture and liturgical reforms.

Simeon I achieved spectacular military and political successes, expanding Bulgarian territory and forcing the Byzantine Empire to recognise the imperial title of the Bulgarian monarchs. The capital Preslav was built in Byzantine fashion to rival Constantinople. Among the city's most remarkable edifices were the Round Church, also known as the Golden Church, and the imperial palace. At that time was created and painted Preslavian pottery, which followed the most prestigious Byzantine models. A chronicle of the 11th century testified that Simeon I had built Preslav for 28 years.

The Byzantine–Bulgarian war of 913–927 (Bulgarian: Българо–византийска война от 913–927) was fought between the Bulgarian Empire and the Byzantine Empire for more than a decade. Although the war was provoked by the Byzantine emperor Alexander's decision to discontinue paying an annual tribute to Bulgaria, the military and ideological initiative was held by Simeon I of Bulgaria, who demanded to be recognized as Tsar and made it clear that he aimed to conquer not only Constantinople but the rest of the Byzantine Empire, as well.

In 917, the Bulgarian army dealt a crushing defeat to the Byzantines at the Battle of Achelous, resulting in Bulgaria's total military supremacy in the Balkans. The Bulgarians again defeated the Byzantines at Katasyrtai in 917, Pegae in 921 and Constantinople in 922. The Bulgarians also captured the important city of Adrianople in Thrace and seized the capital of the Theme of Hellas, Thebes, deep in southern Greece. Following the disaster at Achelous, Byzantine diplomacy incited the Principality of Serbia to attack Bulgaria from the west, but this assault was easily contained. In 924, the Serbs ambushed and defeated a small Bulgarian army on its way to Serbia, provoking a major retaliatory campaign that ended with Bulgaria's annexation of Serbia at the end of that year.

Tsar (/zɑːr, (t)sɑːr/; also spelled czar, tzar, or csar; Bulgarian: цар, romanized: tsar; Russian: царь, romanized: tsar'; Serbian: цар, car) is a title historically used by Slavic monarchs. The term is derived from the Latin word caesar, which was intended to mean emperor in the European medieval sense of the term—a ruler with the same rank as a Roman emperor, holding it by the approval of another emperor or a supreme ecclesiastical official—but was usually considered by Western Europeans to be equivalent to "king".

Tsar and its variants were the official titles in the First Bulgarian Empire (681–1018), Second Bulgarian Empire (1185–1396), the Kingdom of Bulgaria (1908–1946), the Serbian Empire (1346–1371), and the Tsardom of Russia (1547–1721).The first ruler to adopt the title tsar was Simeon I of Bulgaria. Simeon II, the last tsar of Bulgaria, is the last person to have held this title.

The medieval Bulgarian army was the primary military body of the First and the Second Bulgarian Empires, and some Puppet states of the former, like the Despotate of Dobruja. During the first decades after the foundation of the country, the army consisted of a Bulgar cavalry and a Slavic infantry. The core of the Bulgarian army was the heavy cavalry, which consisted of ca. 12,000 heavily armed riders. At its height in the 9th and 10th centuries, it was one of the most formidable military forces in Europe and was feared by its enemies. There are several documented cases of Byzantine commanders abandoning an invasion because of a reluctance to confront the Bulgarian army on its home territory.

The army was intrinsically linked to the very existence of the Bulgarian state. Its success under Tsar Simeon I the Great marked the creation of a wide-ranging empire, and its defeat in a prolonged war of attrition in the early 11th century meant the end of Bulgarian independence. When the Bulgarian state was reestablished in 1185, a series of capable emperors achieved a remarkable string of victories over the Byzantines and the Western Crusaders, but as the state and its army fragmented in the 13th and 14th centuries, it proved unable to halt the Ottoman advance, which resulted in the conquest of all of Bulgaria by 1396/1422. It would not be until 1878, with the Liberation of Bulgaria, that a Bulgarian military would be restored.

The Preslav Literary School (Bulgarian: Преславска книжовна школа), also known as the "Pliska Literary School" or "Pliska-Preslav Literary school" was the first literary school in the medieval First Bulgarian Empire. It was established by Boris I in 886 in Bulgaria's capital, Pliska. In 893, Simeon I moved the seat of the school from the First Bulgarian capital Pliska to the new capital, Veliki Preslav. Preslav was captured and burnt by the Byzantine Emperor John I Tzimisces in 972 in the aftermath of Sviatoslav's invasion of Bulgaria.

A knyaz, also knez, knjaz or kniaz (Church Slavonic: кънѧѕь, romanized: kŭnędzĭ), is a historical Slavic title, used both as a royal and noble title in different times. It is usually translated into English as 'prince', 'king' or 'duke', depending on specific historical context and the potentially known Latin equivalents at the time; the word was originally derived from the common Germanic *kuningaz ('king').

Feminine forms of the word may be divided into two groups: