The history of the country that became modern Bulgaria can be traced back many hundreds of years before the time of Christ, predating by fifteen or more centuries the arrival of the people known as Bulgars, from whom the country ultimately took its name. The earliest people to have a viable political organization in the area were the Thracians, whose loosely organized tribes occupied and controlled much of the Balkan Peninsula. Later, when their society began to disintegrate, the Thracians fell under Greek influence and joined forces with Athens to overrun neighboring Macedonia. In the fourth century B.C., however, Philip of Macedon, competing with the Greeks in a power struggle over Thrace, conquered Thrace and made the Thracians a subject people. This invasion was followed in the second century B.C. by a Roman invasion of Macedonia and a subsequent conquest of Thrace. By the first century A.D. the Romans totally dominated the area. Despite their strict and unpopular military control over the population, under their tutelage cities grew, roads were constructed, and mining and farming were developed. In the third century A.D. a series of mass migrations into the Balkans began; these migrations lasted for several centuries (see ch. 3). The Goths came in four separate waves during the third century. In the fourth century the Huns swept across the country, razing cities and villages. They were followed in the fourth and fifth centuries by the Visigoths and Ostrogoths who, like the Huns, continued to ravage the country. These invasions culminated in the eventual conquest and settlement by the relatively civilized Slavs in the sixth century. In A.D. 330 the Emperor Constantine established what was to be considered a second Rome and named it Constantinople. In this period the Roman Empire in the Balkans was split into two parts: in the east, Thrace was once again under Greek domination, and the west was dominated by the Romans. Constantinople was growing in power, and Greek influence was eroding the political and cultural influence of the Romans. By the mid-fourth century Rome and Constantinople were actively struggling for domination over the Balkans. In the sixth century A.D. the Slavs crossed the Danube River and occupied much of the Balkan Peninsula. Although the Byzantines built fortresses to protect themselves, they were unable to hold the Slavs at bay. Once the Slavs had taken over most of the Balkan Peninsula, they succeeded in destroying the existing social system, rapidly replacing it with their own. Soon the entire Thracian population became slavicized.