The new Roman province was limited to the regions originally inhabited by the Dacians, and a strong garrison, estimated by historians at 25,000 men, was left to guard it.  Numerous colonists from all parts of the Roman Empire were brought here as settlers, and what remained of the Dacian population completely amalgamated with them.  The new province quickly developed under the impulse of Roman civilization, of which numerous inscriptions and other archaeological remains are evidence.  It became one of the most flourishing dependencies of the Roman Empire, and was spoken of as Dacia Felix.

About a century and a half later hordes of barbarian invaders, coming from the north and east, swept over the country.  Under the strain of those incursions the Roman legions withdrew by degrees into Moesia, and in A.D. 271 Dacia was finally evacuated.  But the colonists remained, retiring into the Carpathians, where they lived forgotten of history.

The most powerful of these invaders were the Goths (271-375), who, coming from the shores of the Baltic, had shortly before settled north of the Black Sea.  Unaccustomed to mountain life, they did not penetrate beyond the plains between the Carpathians and the Dnjester.  They had consequently but little intercourse with the Daco-Roman population, and the total absence in the Rumanian language and in Rumanian place-names of words of Gothic origin indicates that their stay had no influence upon country or population.  Material evidence of their occupation is afforded, however, by a number of articles made of gold found in 1837 at Petroasa (Moldavia), and now in the National Museum at Bucarest.

After the Goths came the Huns (375-453), under Attila, the Avars (566-799), both of Mongolian race, and the Gepidae (453-566), of Gothic race—­all savage, bloodthirsty raiders, passing and repassing over the Rumanian regions, pillaging and burning everywhere.  To avoid destruction the Daco-Roman population withdrew more and more into the inaccessible wooded regions of the mountains, and as a result were in no wise influenced by contact with the invaders.

But with the coming of the Slavs, who settled in the Balkan peninsula about the beginning of the seventh century, certain fundamental changes took place in the ethnical conditions prevailing on the Danube.  The Rumanians were separated from the Romans, following the occupation by the Slavs of the Roman provinces between the Adriatic and the Black Sea.  Such part of the population as was not annihilated during the raids of the Avars was taken into captivity, or compelled to retire southwards towards modern Macedonia and northwards towards the Dacian regions.

Parts of the Rumanian country became dependent upon the new state founded between the Balkans and the Danube in 679 by the Bulgarians, a people of Turanian origin, who formerly inhabited the regions north of the Black Sea between the Volga and the mouth of the Danube.