Beginning with the tenth century, documents attest to the existence of state formations throughout Romania’s territory. These formations go by the name of dukedoms, knezdoms and voivodeships, commonly termed by people "tari" (terrae) = lands, countries (Map 11).

The attempts to rebuild old Transylvania-centered Dacia were unsuccessful because of the castward expansion of the Hungarian Kingdom. The Transylvania state formations had reached a high level of organization, and they put up a long and staunch resistance to the military pressure of the Hungarians, but in the end, they had to give in and form one single voivodeship of Transylvania. However, some of its zones continued to have local autonomy. By the end of the eleventh and mainly in the twelfth century, Transylvania gradually fell under Hungarian domination. Nevertheless, it could preserve its own organization, being ruled by a voivode - a specifically Romanian form of government generalized all over Transylvania until the 16th century, when this status was changed into that of prince.

In order to secure the defence of their frontiers against the inroads made by steppe populations (Petchenegs, Cumans, and Tartars) and to exploit the riches of Transylvania more profitably, the Hungarian kings encouraged other groups of people to settle down in the area. This process began in mid-12th century, when groups of Szeklers (a population mix of steppe migrants, who had followed the Hungarians on their way to Europe), and of Saxons (from Flanders, Luxembourg, the Mosel and the Rhine region, and from Saxony) were brought in. The changes that took place in the world early in the 14th century, in the aftermath of the crises that had swept the big states neighbouring Romania, as well as the weakening of the over one-hundred-year-old Golden Horde grip over the Romanian lands that lay south and east of the Carpathians, favoured the emancipation of the Romanian medieval states of Walachia and Moldavia. The leading Romanian circles from Transylvania, then in conflict with the Hungarian Crown, because of the latter’s intentions to dissolve the local autonomies, contributed, in their turn, to the processes of unification unfolding beyond the mountains. As people kept crossing the mountains, a new demographic inflow and further political experience were brought to the southand east Carpathian leaders. The economic exchanges, stimulated by the development of boroughs and of some towns linked, through transit trade routes, with the commercial world abroad, offered a good chance to the Romanian political formations to place their unification projects on a sound and viable basis. Once their independence from the Hungarian Crown had been won in battle, the Romanian Principalities began to play an increasingly important political, military and cultural role in Southeastern and Central Europe. The founders of the independent Romanian states, voivodes Basarab I (1324-1352) in Walachia and Bogdan I (1359-1365) in Moldavia, barred up the Expansionist tendencies of the big neighbouring states and set the guidelines for Romania’s external policy viz, defence of the country’s independence. Romania’s state interests claimed the establishment of solid external ties in all cardinal points;the Romanian countries could not survive and defend their national being unless they fitted into the whole aggregate of external relations. They would decide upon an alliance with one group of forces or another, in terms of where the threat to their existence lay.

The long battles waged by voivodes Mircea the Old (Mircea cel Batran) (1386-1418), Vlad the Impaler (Vlad Tepes) (1456-1462) and Stephen the Great (Stefan cel Mare) ( 1457-1504) against the Otoman Empire enabled Walachia and Moldavia to preserve their state independence. In the end, however (16th century), the two principalities were obliged to accept the Portr’s suzerainty. After the battle of Mohacs (1526) and the fall of the Hungarian Kingdom, Transylvania became an autonomous principality under Ottoman suzerainty, its political regime being similar to that of Walachia and Moldavia. This status would account for enhanced economic and political relations among the Romanian Countries, relations underlain by unity of kin, language, culture, customs and religious belief, favoured also by a unitary geographical space.