DACIA. — By this name, in the imperial period, a vast region of central Europe was understood, between Sarmatia and Germania, roughly bounded on the west by the Tisia (Theiss), on the south and southeast by the Danube, and reaching eastward to the lower course of the Tyras (Dniester) and the Carpathians.
The corresponding modern regions would be Transylvania, Wallachia, and Moldavia. The inhabitants, the Dacians (Dai, Getae), were related by descent and language to the Thracians. Toward the end of the Roman Republic, King Burebista united many of their tribes into a single state and aroused concern by his enterprise, to such an extent that Julius Caesar, proconsul of Cisalpine Gaul and Illyricum, seemed likely to turn his arms against him rather than toward the conquest of Transalpine Gaul. The danger to the Roman frontiers re-emerged a century later, when another energetic ruler, Decebalus, once again held the Dacian tribes together.
During the reign of Domitian, war was repeatedly waged against the Dacians, and not always successfully, so that Trajan had to undertake two
very serious expeditions that led to the complete subjugation of the country (in 1073).
Reduced to a Roman province and provided with roads, military camps, and colonies, it nevertheless did not have very secure frontiers, to such an extent that, as the barbarian pressure became increasingly severe throughout the third century, the emperor Aurelian in 271 decided to withdraw the occupying troops and colonists south of the Danube, giving a part of the province of Moesia, as a charge and a memorial, the name of D.; it was later divided into D. Ripensis along the river and D. Mediterranea around Sardica (Sofia). Within the borders of what had been the province of D., between 107 and 271, soldiers and colonists introduced various religions and cults, and epigraphic texts with dedications to various Greek-Roman, Syrian, and Persian divinities (Mithras) are relatively abundant. Christianity must therefore also have penetrated there, but its traces are scarce, much less abundant, for example, than in nearby Scythia Minor, on the shores of the Black Sea, southeast of the Danube. Mention is made of some funerary inscriptions at Napoca (Cluy, Koloszvar), at Sardica, a sarcophagus in the Belgrade museum, relief crosses near Drobeta, a Christian lamp at Luciu, and a Constantinian monogram on gold bars found at Czofalva in Transylvania (CIL, III, 8080). Even if one accepts, as St. Jerome maintains (Epist., 59), a preaching by St. Paul as far as Illyricum, and even if one accepts the claims of the Church of Sirmium (Mitrovitza) to date back to apostolic times, none of this would concern D., which the Danube separates from Illyricum.
The new D. of Aurelian, that south of the Danube, had bishoprics in the fourth century, among them the flourishing see of Sardica, where a council met in 343, and that of Renesiana, distinguished by the work of its bishop, St. Nicetas (cf. the carmen de Niceta of St. Paulinus of Nola: the Saint speaks of D. Mediterranea and Ripensis, and calls the Dacians on the opposite bank Getae).
In the time of Justinian, a bishop of Aquae in D. Ripensis is known, whose jurisdiction also extended over places on the left bank of the Danube.