The so-called Free Dacians () is the name given by some modern historians to those Dacians who putatively remained outside, or emigrated from, the Roman Empire after the emperor Trajan's Dacian Wars (AD 101-6). Dio Cassius named them Dakoi prosoroi (Latin: Daci limitanei) meaning "neighbouring Dacians".
A population of Dacians existed on the fringes of the Balkan Roman provinces, especially in the eastern Carpathian Mountains, at least until about AD 340. They were responsible for a series of incursions into Roman Dacia in the period AD 120-272, and into the Roman Empire south of the Danube after the province of Dacia was abandoned by the Romans around AD 275.
Traditional paradigm
According to many scholars, amongst the Free Dacians were refugees from the Roman conquest, who had left the Roman-occupied zone, and some Dacian-speaking tribes resident outside that zone, notably the Costoboci and the Carpi in SW Ukraine, Moldavia and Bessarabia. The refugees may have joined these resident peoples. Through proximity with the Roman province of Dacia, the Free Dacians supposedly became Romanised and adopted the Latin language and Roman culture. Despite this acculturation, the paradigm holds that the Free Dacians were irredentists, repeatedly invading the Roman province in attempts to recover the refugees' ancestral land. They were unsuccessful until the Roman province was abandoned by the emperor Aurelian in AD 275. After this, the Free Dacians supposedly liberated the Roman province and joined the remaining Romano-Dacians to form a Latin-speaking Daco-Roman ethnic group that were the forebears of the modern Romanian people.
Validity of paradigm
There is substantial evidence that large numbers of ethnic Dacians continued to exist on the fringes of the Roman province of Dacia. During Trajan's Dacian Wars in AD 102 and AD 106, enormous numbers of Dacians were killed or taken into slavery. It also appears that many indigenous Dacians were expelled from, or emigrated from, the occupied zone. Two panels of Trajan's Column depict lines of Dacian peasants leaving with their families and animals at the end of each war.
Furthermore, it appears that the Romans did not permanently occupy the whole of Decebal's kingdom. The latter's borders, many scholars believe, are described in Ptolemy's Geographia: the rivers Siret in the east, Danube in the south, Thibiscum (Timiş) in the west and the northern Carpathian Mountains in the north. But the eastern border of the Roman province was by AD 120 set at the Limes Transalutanus ("Trans-Olt Frontier"), a line to the just east of the river Aluta (Olt), thus excluding the Wallachian plain between the limes and the river Siret. In Transylvania, the line of Roman border-forts seems to indicate that the eastern and northern Carpathians were outside the Roman province.
The unoccupied sections of Decebal's kingdom are likely to have been inhabited predominantly by ethnic Dacians, although according to Ptolemy, the northernmost part of the kingdom (northern Carpathians/Bukovina) was shared by non-Dacian tribes: the Anartes and the Taurisci, who were probably Celtic, and the Germanic Bastarnae are also attested in this region. Furthermore, some areas were occupied after 106 by nomadic Sarmatian tribesmen, most likely a minority ruling over the sedentary Geto-Dacian majority e.g. Muntenia (eastern Wallachia), which was ruled by the Roxolani Sarmatians and possibly also northern Moldavia, which was under the Costoboci, a dacian tribe. But there are no reports of Sarmatians controlling the remaining unoccupied region of Decebal's kingdom between the Transylvanian border of the Roman province and the Siret, i.e. the eastern Carpathians, and it is therefore in these mountain valleys and foothills that the politically independent Free Dacians were most likely concentrated, and presumably where most of the refugees from the Roman conquest escaped to.