The land now known as Bulgaria had attracted human settlement as early as the Bronze Age.

Almost from the first, however, existing civilizations had been challenged by powerful neighbors.

The first known civilization to dominate the territory of present- day Bulgaria was that of the Thracians, an Indo-European group.

Although politically fragmented, Thracian society is considered to have been comparable to that of Greece in the arts and economics; these achievements had reached a peak in the sixth century BCE.

Because of political disunity, however, Thrace then had been successively occupied and divided by the Greeks, the Persians, the Macedonians, and the Romans.

After the decline of the Macedonian Empire of Alexander the Great, a new Thracian kingdom had emerged in the third century BCE.

Occupied by the Romans, it had remained a kingdom within the Roman Empire until the emperor Vespasian incorporated it as a district in the first century CE.

Roman domination has brought orderly administration and the establishment of Serditsa (on the site of modern Sofia) as a major trading center in the Balkans.

In the fourth century CE, when the Roman Empire splits between Rome and Constantinople, Thrace becomes part of the Eastern, or Byzantine, Empire.

Christianity is introduced to the region at this time.

Both the Latin culture of Rome and the Greek culture of Constantinople will remain strong influences on ensuing civilizations.