First Bulgarian Empire

The First Bulgarian Empire was a medieval Bulgarian state that existed in southeastern Europe between the 7th and 11th centuries AD. It was founded circa 681 when Bulgar tribes led by Asparukh moved to the north-eastern Balkans. At the height of its power, Bulgaria spread from the Danube Bend to the Black Sea and from the Dnieper River to the Adriatic Sea.

Samuel's Fortress in Ohrid

The Bulgars were semi-nomadic warrior tribes originating from Central Asia. Between 630 and 635 Khan Kubrat of the Dulo clan managed to unite the main Bulgar tribes and to declare independence from the Avars.  Kubrat, who was baptised in Constantinople in 619, concluded an alliance with the Byzantine Emperor Heraclius (r. 610–641) and the two countries remained in good relations until Kubrat's death between 650 and 663. After his demise Old Great Bulgaria disintegrated under strong pressure in 668.

The Bulgarian colonies after the fall of Old Great Bulgaria in the 7th century

In 680 the Byzantine Emperor Constantine IV (r. 668–685), having recently defeated the Arabs, led an expedition at the head of a huge army and fleet to drive off the Bulgars but suffered a disastrous defeat at the hands of Asparukh at Onglos.  In 681, the Byzantines were compelled to sign a humiliating peace treaty, forcing them to acknowledge Bulgaria as an independent state.

Constantine IV and his retinue, mosaic in basilica of Sant'Apollinare in Classe, Ravenna.

The Bulgars were superior organisationally and militarily and came to dominate politically the new state but there was cooperation between them and the Slavs for the protection of the country. To the north-east the war with the Khazars persisted and in 700 Khan Asparukh perished in battle with them. Despite this setback the consolidation of the country continued under Asparukh's successor, Khan Tervel (r. 700–721).

Khan Tervel

In 705 Khan Tervel assisted the deposed Byzantine Emperor Justinian II to regain his throne in return of the area Zagore in Northern Thrace, which was the first expansion of Bulgaria to the south of the Balkan mountains. In addition Tervel obtained the almost imperial title Caesar and sitting enthroned besides the Emperor received the obeisance of the citizenry of Constantinople and numerous gifts.  However, three years later Justinian tried to regain the ceded territory by force, but his army was defeated at Anchialus.

Battle of Anchialus

Skirmishes continued until 716 when Khan Tervel signed an important agreement with Byzantium that defined the borders and the Byzantine tribute. When the Arabs laid siege to Constantinople in 717–718 Tervel dispatched his army to help the besieged city. In the decisive battle before the Walls of Constantinople the Bulgarians slaughtered around 22,000 Arabs forcing them to abandon the undertaking.

Section of wall of Constantinople

With the demise of Khan Sevar (r. 738–753) the ruling Dulo clan died out and the Khanate fell into a long political crisis during which the young country was on the verge of destruction. In just fifteen years seven Khans reigned, and all of them were murdered. The internal instability was used by the "soldier Emperor" Constantine V (r. 745–775), who launched nine major campaigns aiming to eliminate Bulgaria.

Constantine V(on the right) and his father Leo III the Isaurian(on the left)