The country was founded in the 7th century. Prior to that, it was occupied by the Greeks, Romans, and Byzantines.
The Soviets held strong sway over the country (and broader region) following their ‘liberation’ of the country from the Ottoman Empire. Since the fall of the USSR, the Bulgarians have joined NATO and aligned themselves closer to the West.
Sofia: Romans called the city Serdica. The capital is full of Jewish, Christian, and Islamic sites. Emperor Galerius issued the Edict of Toleration in 311 AD.