Bulgaria is one of the most ancient countries in Europe.
The First Bulgarian Empire became known simply as Bulgaria since its recognition by the Byzantine Empire in 681. Some historians use the terms Danube Bulgaria, First Bulgarian State, or First Bulgarian Tsarstvo .
It is likely that the original Bulgars were greatly outnumbered by the Slavic population among whom they were settled. Between the 7th and the 10th centuries, the Bulgars gradually became absorbed by the Slavs, adopting a South Slav languageand converting to Christianity (of the Byzantine rite) under Boris I of Bulgaria in 864. Modern Bulgarians are normally considered to be of Southern Slavic origin. However, the Slavs were only one of the communities that had been present in the area conquered by Bulgars, themselves being recent migrants in the Balkans. Several other peoples were eventually absorbed into the new ethnicity. At that time the process of absorption of the remnants of the old Thraco-Roman and Thraco-Byzantine population had already been significant in the formation of this new ethnic group. The new single identity nation would continue to identify as Bulgarian and uphold the eponymous state as its own. Modern Bulgarians continue to celebrate the original non-Slavic Bulgar state and Thracian ancestors, while embracing a Slavic identity at the same time.
In 864 the Byzantines under Michael III invaded Bulgaria on suspicions that Khan Boris I prepared to accept Christianity in accordance with the Western rites. Upon the news of the invasion, Boris I started negotiations for peace. The Byzantines returned some lands in Macedonia and their single demand was that he accept Christianity from Constantinople rather than Rome. Khan Boris I agreed to that term and was baptised in September 865 assuming the name of his godfather, Byzantine Emperor Michael, and became Boris-Mihail. The pagan title "Khan" was abolished and the title "Knyaz" assumed in its place. The reason for the conversion to Christianity, however, was not the Byzantine invasion. The Bulgarian ruler was indeed a man of vision and he foresaw that the introduction of a single religion would complete the consolidation of the emerging Bulgarian nation, which was still divided on a religious basis.[neutrality is disputed] He also knew that his state was not fully respected by Christian Europe and its treaties could have been ignored by other signatories on religious basis.
Although the Bulgarian Knyaz succeeded in securing an autonomous Church, its higher clergy and theological books were still Greek, which impeded the efforts to convert the populace to the new religion. Between 860 and 863 the Byzantine monks of Greek origin Saint Cyril and Saint Methodius created the Glagolitic alphabet, the first Slavic alphabet by order of the Byzantine Emperor, who aimed to convert Great Moravia to Orthodox Christianity. However, these attempts failed and in 886 their disciples Clement of Ohrid, Naum of Preslav and Angelarius, who were banished from Great Moravia, reached Bulgaria and were warmly welcomed by Boris I.
The Second Bulgarian Empire ( Vtorо Bălgarskо Tsartsvo) was a medieval Bulgarian state that existed between 1185 and 1396 or 1422. A successor to the First Bulgarian Empire, it reached the peak of its power under Tsars Kaloyan and Ivan Asen II before gradually being conquered by the Ottomans in the late 14th and early 15th centuries. It was succeeded by the Principality and later Kingdom of Bulgaria in 1878.
The Second Bulgarian Empire was a centre of a thriving culture that reached its peak in the mid-to-late 14th century during the reign of Ivan Alexander (r. 1331–71). Bulgarian architecture, arts, and literature spread beyond the borders of Bulgaria into Serbia, Wallachia, Moldavia, and the Russian principalities and had an impact on Slavic culture. Bulgaria was influenced by the contemporaneous Byzantine cultural trends. The main cultural and spiritual centre was Tarnovo, which grew into a "Second Constantinople" or "Third Rome".Bulgarian contemporaries called the city "Tsarevgrad Tarnov", the Imperial city of Tarnovo, after the Bulgarian name for Constantinople—Tsarigrad. Other important cultural hubs included Vidin, Sofia, Messembria, and a large number of monasteries throughout the country.
The Second Bulgarian Kingdom existed till the fall by Otomans in 1395.
The history of Ottoman Bulgaria spans nearly 500 years, from the conquest by the Ottoman Empire of the smaller kingdoms emerging from the disintegrating Second Bulgarian Empire in the late 14th century, to the Liberation of Bulgaria in 1878. As a result of the Russo-Turkish War (1877–1878), the Principality of Bulgaria, a self-governing Ottoman vassal state that was functionally independent, was created. In 1885 the autonomous province of Eastern Rumelia came under the control of the Bulgarian Tsar. Bulgaria declared independence in 1908.
It was the beginning of 3rd Bulgarian Country which lasts till now.