Geography

Between the establishment of the First Bulgarian Empire in 681 and the Ottoman conquest of the late fourteenth century, Bulgarian rulers governed territories that changed repeatedly across the Danube basin and the Balkan Peninsula. At different times, their authority reached from the lower Danube and Black Sea toward the middle Danube and Adriatic. These were not borders corresponding to modern Bulgaria. Nor were the two empires one continuous state: Byzantine rule followed the First Empire’s defeat in 1018, and Bulgarian independence was restored in 1185.

Geography shaped where rulers could gather resources, defend frontiers, and connect communities. The Danube, the Balkan Mountains, broad plains, and routes through mountain passes offered both barriers and corridors. Over the centuries, the political map changed alongside the balance between central authority and regional powers, while communities with different languages and traditions lived within and around the empires.

On this page5 sections

The Danube and the first Bulgarian state

The First Bulgarian Empire began when the Bulgars led by Asparuh moved west to the lower Danube and then crossed the river into Byzantine territory south of it. The delta and surrounding grasslands offered grazing for their herds. After a military defeat in 680, the Byzantine government recognized the new state in 681 and accepted Bulgarian settlement in lands north of the Balkan Mountains. This placed the early state across the lower Danube, with the river serving both as a frontier and as a route linking communities on its banks.

The region was not empty. Slavic communities already lived across much of the Balkans, alongside populations descended from earlier inhabitants, including Thracians who had become Romanized or Hellenized in different areas. The new state’s ruling Bulgar group held political and military authority, while Slavic groups initially retained local leaders and customs in return for obligations to the state. The relationship developed over time rather than remaining a fixed division between two peoples.

The Balkan Mountains separated the northern lands, often described as Moesia, from Thrace to the south. Their passes could be difficult for invading armies to cross, but also connected the regions. In 705, the ruler Tervel gained Zagore in northern Thrace, extending Bulgarian authority south of the mountains. Under Krum in the early ninth century, the state expanded west along the middle Danube after the Avar Khaganate collapsed. Later rulers extended control into Macedonia and toward the Adriatic. The results were a larger, more varied territory, not a single frontier that remained stable.

Expansion and shifting western and southern frontiers

During the ninth and early tenth centuries, Bulgarian power expanded through Macedonia and across large parts of the Balkans. Control of towns and routes extended the court’s reach towards the Adriatic, while conflict with Byzantium repeatedly shifted the southern frontier. Inland authority rested on fortresses, officials and local leaders whose allegiance connected the intervening country to the ruler.

Territorial power could contract as quickly as it grew. In the late tenth century, invasion by the Kievan Rus and subsequent Byzantine campaigns brought the eastern parts of the empire under Byzantine control. Bulgarian resistance continued in the west, where Samuel built a centre of power and recovered territory for a time. Byzantine conquest was completed in 1018. During the last years of the First Empire, political centres shifted westward from Pliska and Preslav toward places including Skopje, Ohrid, and Bitola, reflecting the changing geography of power as well as military pressure.

From 1018 to 1185, the former Bulgarian lands were under Byzantine rule, although major rebellions broke out. The Second Bulgarian Empire emerged from a revolt centred on Tarnovo in 1185. Much of Moesia, north of the Balkan Mountains, joined the rebels, who also secured aid from Cumans, a Turkic people living north of the Danube. The river was therefore not simply a dividing line: movement across it could bring allies and forces into the Balkan conflicts.

The Second Empire across the Balkans

From its base in Moesia, the Second Empire expanded south into Thrace and west toward Macedonia and the central Balkans. Tarnovo, on the Yantra River and within a landscape of hills and mountain approaches, became its capital. The surrounding terrain gave the capital defensible positions, while routes through the mountains connected it to the plains and southern regions. Rulers also relied on a network of fortresses to guard approaches and secure important territories.

Under Kaloyan and Ivan Asen II, Bulgarian power again extended over a wide area. After Ivan Asen II’s victory over the ruler of Epirus in 1230, towns and territories from Adrianople in Thrace toward Durazzo on the Adriatic recognized his rule. The empire also held lands toward the Black Sea. Its authority covered regions with different local histories and communities; it did not make those regions culturally or linguistically uniform.

After the mid-thirteenth century, invasions and conflict with neighboring powers, including Mongols, Byzantines, Hungarians, and Serbs, weakened central control. Some nobles gained considerable independence, and the empire’s frontiers repeatedly contracted and shifted. There was a recovery in the fourteenth century, but by Ivan Alexander’s death in 1371, the country had divided among rival centres of authority. Tarnovo held the central realm, Vidin was a separate power in the northwest, and Dobrotitsa controlled a coastal domain associated with Karvuna. This fragmentation left the region less able to resist Ottoman expansion. Tarnovo fell in 1393 and Vidin in 1396; claims to Bulgarian imperial authority continued afterward, but did not restore the former territorial unity.

Regional communities and changing languages

Political membership, language, and identity did not correspond neatly to one another. The early state was ruled by Bulgars and included numerous Slavic communities as well as people from older Balkan populations. Over time, the ruling Bulgars adopted the increasingly prevalent Slavic language. By the ninth century, the language of the state and its population had changed substantially, while Bulgar political traditions and titles remained part of the empire’s institutions.

Christianization under Boris I in 864 created a shared religious framework, but it also raised a practical question: which language would serve the church and state? Old Church Slavonic, the earliest Slavic literary language, had been standardized by the Byzantine missionaries Cyril and Methodius for Christian teaching. Its basis was a Slavic dialect associated with the region around Thessaloniki. Bulgarian rulers and scholars developed its use within the empire. Royal patronage after 893 established it as a leading language of worship and literary work.

Preslav in the east and Ohrid in the southwest supported clergy, translation and religious writing. Old Church Slavonic provided a common literary language that could travel with books and trained clergy across regional speech communities. Greek remained important in dealings with Byzantium. Romance-speaking communities, later commonly called Vlachs in the sources, preserved languages descended from Latin in the wider Balkan landscape.

In the Second Empire, written Bulgarian developed from earlier Church Slavonic traditions. Patriarch Euthymius and the Tarnovo scholarly community promoted the correction of religious texts and more consistent spelling in the fourteenth century. Books produced or revised in this setting carried a literary practice beyond the political borders of the Tarnovo realm.

Cumans, Vlachs, and cross-border connections

Communities beyond the Danube affected the political geography of both empires. The Cumans helped the leaders of the 1185 revolt and became an important part of the Second Empire’s military forces. Cuman cavalry served in campaigns, and some Cuman leaders entered the Bulgarian nobility or held high military and administrative posts. Their participation shows how rulers built alliances and armies across the Danube frontier.

Some contemporary descriptions referred to the Second Empire as a state of both Bulgarians and Vlachs. The name of a polity could therefore reflect more than one community, but such labels did not define fixed territorial borders or map directly onto modern national categories. The empires also faced both Latin and Greek powers. First Bulgarian rulers negotiated with Rome over church authority, while Second Empire rulers fought the Latin Empire established at Constantinople after the Fourth Crusade. These political and religious contacts crossed the same shifting Balkan frontiers that shaped military campaigns and regional rule.