After 1204, when Constantinople was conquered by the Western "Crusaders" (named Latini), the Papacy had apparently the best opportunity to put an end to the so-called Eastern Schism. The direct control over the center of the Eastern "Commonwealth" could mean the dissolution of the Greek Patriarchate of Constantinople, the subordination of the Orthodox hierarchy to Rome and, in the future, the bringing back to unity of all Eastern Churches, in all respects (including the rite)(1). This fact would have led soon to the transformation of the great number of Eastern Christians, considered as "schismatics" (Albanians, Bulgarians, Greeks, Romanians, Russians, Serbs, etc.), into Catholics. However, the course of events was different and the "great schism," officialized in 1054, was not only maintained but became even deeper. It is tempting to try to find an answer to the question: How did this situation come about?
Naturally, the "Latin" domination of Constantinople lasted a brief period of time, only about 50 years (1204-1261), and the return of the Byzantine (Greek) authorities in 1261 completely changed these Western plans. On the other hand, the Orthodox hierarchy was far from accepting the subordination as a fait accompli; on the contrary, it started a "resistance" which proved quite efficient in the long run. After all, the Orthodox nations situated in Eastern and Southeastern Europe refused to accept the spontaneous transition to Catholicism merely because the Byzantine center was in Western hands. Another negative fact was the great invasion of the Tatars (1241-1242) and their domination in the region of the Lower Danube. The Papacy did not submit so easily to this situation and, in spite of the Tatars and the Orthodox presence in Constantinople, Rome continued its proselytizing work in the area after 1261. The idea of a uniform and unified church, following the Catholic model, was sustained in a very strict way in the fourteenth century during the time of the Avignon Popes (1309-1377).
When the Union decided by the Council of Lyon (1274) was rejected by the population and by the Greek clergy, the Papacy considered that the only two efficient paths to follow were a new "crusade" against Constantinople and the total subordination, in all respects, of the Eastern Church. Therefore, the period of the Avignon Papacy was the time of the greatest intransigence of the Catholic West towards the Orthodox East as far as the imposition of the religious Union is concerned.(2)
We can't say here why the Greeks or other Orthodox peoples were not attracted to Catholicism during the fourteenth century. Some attempts and even some temporary successes existed, especially after 1354 (when the Turks conquered a piece of land in Europe for the first time), as a Christian reaction against the Ottoman danger. But we will address the special case of the Romanians - the largest nation in Southeastern Europe. For the Romanians, in comparison with the Greeks and the Slavs, some particular circumstances existed, which could have encouraged their union with the Roman Catholic Church. First of all, their great majority was geographically situated within and around the Carpathian chain, namely exactly on the North-Western limit of the Orthodox area, where the Catholic influence was very strong. Secondly, the Romanians were of Roman origin and, at least some of them (the elite), were aware of this fact: they asserted their Latin heritage, they were proud of that and this reality was well known in Catholic circles.(3) In the third place, the Romanians' ancestors became Christians ab antiquo (starting in the second and third centuries) and the new faith was transmitted in Latin. The most important Christian terms in Romanian (Dumnezeu, biserica, cruce, crestin, cuminecatura, inger, pacat, rugaciune, Craciun, Florii, Pasti, Rusalii, etc.) were inherited from Latin. That is why the Romanians, as the sole important representative of the Eastern Roman world, had a special place in this part of Europe. …