One of the earliest societies in the lands of modern-day Bulgaria was the NeolithicKaranovo culture, which dates back to 6,500 BC. In the 6th to 3rd century BC the region was a battleground for Thracians, Persians, Celts and ancient Macedonians; stability came when the Roman Empire conquered the region in AD 45. The Eastern Roman, or Byzantine, Empire lost some of these territories to an invading Bulgar horde in the late 7th century. The Bulgars founded the First Bulgarian Empire in AD 681, which dominated most of the Balkans and significantly influenced Slavic cultures by developing the Cyrillic script. This state lasted until the early 11th century, when Byzantine emperor Basil II conquered and dismantled it. A successful Bulgarian revolt in 1185 established a Second Bulgarian Empire, which reached its apex under Ivan Asen II (1218–1241). After numerous exhausting wars and feudal strife, the Second Bulgarian Empire disintegrated in 1396 and its territories fell under Ottoman rule for nearly five centuries.
Since adopting a democratic constitution in 1991, the sovereign state has been a unitaryparliamentary republic with a high degree of political, administrative, and economic centralisation. The population of seven million lives mainly in Sofia and the capital cities of the 27 provinces. The population has declined since the late 1980s.
The name Bulgaria is derived from the Bulgars, a tribe of Turkic origin that founded the country. Their name is not completely understood and is difficult to trace back earlier than the 4th century AD, but it is possibly derived from the Proto-Turkic word bulģha ("to mix", "shake", "stir") and its derivative bulgak ("revolt", "disorder"). The meaning may be further extended to "rebel", "incite" or "produce a state of disorder", and so, in the derivative, the "disturbers". Ethnic groups in Inner Asia with phonologically similar names were frequently described in similar terms: during the 4th century, the Buluoji, a component of the "Five Barbarian" groups in Ancient China, were portrayed as both a "mixed race" and "troublemakers".