Each of Transylvania's three principal nationalities is divided across two or more religions. Most Transylvanian Romanians belong to either the Romanian (Eastern) Orthodox church or the Uniate church (a hybrid of Eastern Orthodoxy and Roman Catholicism that the Habsburgs created in the late 1600s, with the aim of Catholicizing Transylvania's Romanians) . Some Transylvanian Romanians stayed with the Uniate church even after the Communists forcibly rejoined it with the Orthodox Church in 1948. In addition, as of about 1960 small but growing numbers of Romanians converted to one or another Protestant sect, of which the most significant are the Pentecostals, Seventh-Day Adventists, Jehovah's Witnesses, and Baptists. Among the other ethnic groups, only Serbs share the Orthodox religion with Romanians; the faiths practiced by Romanians are otherwise unique to them. Hungarians in Transylvania have historically belonged to three faiths: Roman Catholicism, Calvinism, and Unitarianism. Swabian Germans were generally (although not universally) Roman Catholic, and Saxons were Lutheran. These historical Religious attachments diminished to some extent during the Communist period as secularization and official atheism eroded religious practice. The different faiths continue, However, to be more or less exclusive to the different ethnic groups, only Roman Catholicism being shared (by some Hungarians and some Swabians). (While both Serbs and Romanians are Orthodox, each group orients to its own patriarch—of, respectively, the Serbian and Romanian Orthodox Churches.)
The history of the different groups in Transylvania is the area of greatest disagreement between Romanians and Hungarians. Few facts are beyond dispute. It seems certain that the ancestral population of modern Romanians derives from the mixture of two groups on the territory of Transylvania: Dacians, an important group at the margins of the Roman Empire, and Romans, who conquered the territory of the Dacians in A.D. 105-106 and brought in substantial numbers of colonists to fortify this easternmost border of the empire. Admixtures of Slavs during their migrations of the seventh to eighth centuries further augmented Romania's heritage. Hungarians arrived in the Danube basin at the end of the ninth century A.D. (the date usually accepted is 896) and, having established their control over the plains in what is now central and eastern Hungary, gradually moved into the Transylvanian region during the tenth and eleventh centuries, consolidating their hold over it by the twelfth century. Disagreement begins here, centering on whether or not a population ancestral to today's Romanians was already inhabiting the area when the Hungarians moved in. Hungarian histories claim that the territory Hungarians settled was empty, the local population having moved out with the Roman retreat from Dacia in 271; Romanians claim that their forebears had stayed in Transylvania, perhaps not in the open spaces but in the foothills, where they had retreated to escape the nomads (Goths, Avars, Khazars, etc.) whose invasion had prompted the Roman retreat. It is difficult to adjudicate between these positions. The way of life of ancestral Romanians did not readily lend itself to producing concrete remains for archaeologists to find. Although both sides invoke archaeology to support their positions, the degree of political investment and patriotic sentiment even among outstanding scholars on both sides obviates neutral scientific interpretation. The matter is further complicated by the fact that the ethnic labels "Hungarian" and "Romanian" as now understood are inapplicable to the tenth and eleventh centuries; current theories of ethnic processes do not unequivocally support the notion that these ethnic groups formed in antiquity and evolved with no changes in their identity into the present, as both Hungarian and Romanian sides presume.
The argument between Hungarians and Romanians Concerning first settlement of Transylvania is linked to their claims to the territory. Following the Hungarian conquest, Transylvania became the eastern rampart of the Hungarian kingdom; it was ruled by a voivod, or military leader, charged with defending Christian Hungary from the Mongols, Petchenegs, Cumans, and other groups raiding from the Asian steppes. The cultured and largely Hungarian nobility of the region participated in the glories of the Renaissance courts of the Hungarian kings; speakers of Romanian, by contrast, were illiterate and uncultured serfs. The region gained importance for Hungarians following the defeat of their army by the Ottomans in 1526, after which the kingdom's center of gravity moved into the Transylvanian hills that the Turks did not manage to subdue fully. For Hungarians, Transylvania was an integral part of their historical kingdom and ought to have remained part of it into the present. By the time population statistics began to be collected in the 1700s, however, Romanians outnumbered Hungarians and Germans; to the argument based on numbers the Romanians added their own historical arguments, marshaling scraps of documentary Evidence from medieval Hungarian and Byzantine sources to buttress their claim that Romanians had been constantly present since the Roman conquest. At first, the goal of this argument was to obtain civic rights for Romanians in Hungary, not to bring the territory under Romanian control. Only late in the nineteenth century did Romanians begin to demand that Transylvania be severed from Hungary and joined with the kingdom of Romania. This was finally accomplished in the wake of World War I, as the victorious powers awarded Transylvania to their Romanian allies (Hungary had been on the losing side). This award was seen by Romanians as the just recognition of their historic rights and by Hungarians as the unjust usurpation of theirs. Between these two exclusive claims, each with its accompanying arsenal of scientific and historical arguments, there is no easy reconciliation.
The history of the German presence in Transylvania is less contested. During the twelfth and thirteenth centuries, Hungary's kings invited colonists from the Rhineland and Flanders to settle in Transylvania, granting them privileges and self-governance; their role was to secure the eastern borderland of the Hungarian kingdom, increase agricultural output, and serve as a counterweight to the power of certain Hungarian nobles. These settlers formed the ancestral Population of the Saxons. Several centuries later, following Austrian expulsion of the Ottomans from Hungary, Habsburg emperors brought a second series of colonists from the area around the Black Forest, settling them in the eastern plain of the Danube basin (the Banat). Once again, the aim was to secure otherwise vulnerable spaces, increase agricultural productivity, and provide a counterweight to the powerful nobles of Hungary. The descendants of these settlers were the modern-day Swabians (found not only in Transylvania but also in eastern Hungary and northern Yugoslavia). On the question of Romanian-Hungarian priority in Transylvania, German-language scholarship tended to take the Hungarian side when Transylvania was part of Hungary, later becoming somewhat more equivocal.