The Thracians were one of the first peoples to settle in Bulgaria.
The Romans arrived in the first century.
Four centuries later, Bulgaria became part of the Byzantine empire.
From the fourteenth century onward, the country was part of the Ottoman empire.
That lasted until the end of the nineteenth century, when the country was liberated by Russia.
At this point for some reason, the Bulgarians thought they ought to have a monarchy.
That whole monarchy thing only lasted until the end of the second world war. Then they gave communism a whirl.
Finally they got with the democracy programme.