Catholic Ukraine and Belarus

What would have been the fate of the Polish Lithuanian Commonwealth had the Ukrainians and Byelorussians under there control converted to the dominant faith, maybe there languages adopting latin alphabet? Maybe this happens by late 16th/early 17th centuries.

Would Russia still be able to conquer these territories and maybe a reconversion takes place, or would this newly hostile population be too hostile to control?

What does this mean for catholicism in general?
 
What would have been the fate of the Polish Lithuanian Commonwealth had the Ukrainians and Byelorussians under there control converted to the dominant faith, maybe there languages adopting latin alphabet? Maybe this happens by late 16th/early 17th centuries.

Would Russia still be able to conquer these territories and maybe a reconversion takes place, or would this newly hostile population be too hostile to control?

What does this mean for catholicism in general?
What if the Kievan Rus become Catholic instead of Orthodox ?
 
What would have been the fate of the Polish Lithuanian Commonwealth had the Ukrainians and Byelorussians under there control converted to the dominant faith, maybe there languages adopting latin alphabet? Maybe this happens by late 16th/early 17th centuries.

Would Russia still be able to conquer these territories and maybe a reconversion takes place, or would this newly hostile population be too hostile to control?

What does this mean for catholicism in general?
But it already happened, right before partitons most of Byelorussia and Ukraine was at least nominally Greek Catholic (uniate). But assuming that you mean straight up conversion to Roman Catholicism, it requires PLC wank, where PLC is capable of maintaining professional administration, army strong enough to beat Russians and probably it going absolutist (as even UK-type monarchy wouldn't dare to convert that much of a population). So to fulfill these requirements, you need to create a situation where Russia isn't able to conquer them, and if it happens it late 16th/early 17th century catholicisation + latin alphabet + political Polish control, means that there would be massive polonisation (Old Ruthenian written in Latin alphabet was often mistaken for Polish) and probably it'd mean that "Byelorussian" and "Ukrainian" would be just regional variety of "Pole" as "Kashubian" or "Silesian" is right now. @Jan Olbracht
 
In theory Belarus and Ukraine WERE mostly Catholic by late 18th century (Byzantine Rite Catholic), of course Union of Brest was hardly noticed by Ruthenian peasants (they were not aware that they suddenly became Catholic) but same thing happened in Prussia, when peasants without even noticing it switched from Catholicism to Lutheranism. In Austrian Galizia, when Union was not delegalised, vast majority of Ukrainians remained Byzantine Rite Catholic, same would happen if Ukraine remained part of PLC.
 
But it already happened, right before partitons most of Byelorussia and Ukraine was at least nominally Greek Catholic (uniate).
By the time of the 1st Partition the Eastern Ukraine was not a part of the PLC for more than a century so what you are saying applies only to Belorussia and Right Bank Ukraine. Not sure if the Unitas had been a majority even on paper because the ideological justification of CII was oppression of the Orthodox Christians on the PLC territory. Not sure if even formally the majority had been Unitas: a considerable part of the top level clergy were not (hence their requests for help) and the peasants probably did not have a clue unless their local church was looted. 🤪
 
In theory Belarus and Ukraine WERE mostly Catholic by late 18th century (Byzantine Rite Catholic), of course Union of Brest was hardly noticed by Ruthenian peasants (they were not aware that they suddenly became Catholic) but same thing happened in Prussia, when peasants without even noticing it switched from Catholicism to Lutheranism. In Austrian Galizia, when Union was not delegalised, vast majority of Ukrainians remained Byzantine Rite Catholic, same would happen if Ukraine remained part of PLC.
“The union was not accepted by all the members of the Ruthenian Orthodox Church in these lands, and marked the creation of Greek Catholic Church and separate eparchies that continued to stay Orthodox among which were Lviv eparchy, Peremyshel eparchy, Mukachevo eparchy and Lutsk eparchy that at first accepted the union but later oscillated back and forth.” It seems that by mid-XVII at least Eastern Ukraine was predominantly Orthodox (hence appeal to Moscow during Khmelnitsky Uprising) and even in the mid-XVIII the Orthodox had been prevailing at least in some areas of Right Bank Ukraine and Belorussia.
 
By the time of the 1st Partition the Eastern Ukraine was not a part of the PLC for more than a century so what you are saying applies only to Belorussia and Right Bank Ukraine. Not sure if the Unitas had been a majority even on paper because the ideological justification of CII was oppression of the Orthodox Christians on the PLC territory. Not sure if even formally the majority had been Unitas: a considerable part of the top level clergy were not (hence their requests for help) and the peasants probably did not have a clue unless their local church was looted. 🤪
I said "most of Ukraine" not all of Ukraine and right-bank Ukraine, Volhynia and Ruthenia fulfill this requirement, don't they? There was Mstislav bishopric which was still majority Orthodox and "hajdamaks" in right-bank Ukraine still considered themselves Orthodox and it was enough for CII to create justification, after all we're talking about a person who took part in killing her husband, usurped her own son and made up the tale about Peter being mentally ill and Paul not being his son, I don't expect her propaganda to describe truth reliably. After all, I agree with your "peasants not having a clue" but most of top clergy had been uniate - when you're referring the events of "koliszczyzna", Melchizedek Jaworski (the Orthodox guy who asked for help) wasn't born in PLC and he was only claiming to be a bishop in right-bank Ukraine, and his claim was opposed by local clergy. And any scenario (though not necessary as wankish as I described before) of catholicisation of Ukraine and Belarus lasting into XXIth century requires PLC not becoming mockery of the state which it became in XVIIIth century OTL.
 
“The union was not accepted by all the members of the Ruthenian Orthodox Church in these lands, and marked the creation of Greek Catholic Church and separate eparchies that continued to stay Orthodox among which were Lviv eparchy, Peremyshel eparchy, Mukachevo eparchy and Lutsk eparchy that at first accepted the union but later oscillated back and forth.” It seems that by mid-XVII at least Eastern Ukraine was predominantly Orthodox (hence appeal to Moscow during Khmelnitsky Uprising) and even in the mid-XVIII the Orthodox had been prevailing at least in some areas of Right Bank Ukraine and Belorussia.
Loss of Eastern Ukraine actually helped to strenghten Byzantine Rite in PLC's part of Ukraine during 18th century. With rise of Ukrainian nationalism Byzantine Rite would be seen as part of Ukrainian national identity-like IOTL in Galizia-something, that makes Ukrainians different from both Poles and Russians.
 
What would have been the fate of the Polish Lithuanian Commonwealth had the Ukrainians and Byelorussians under there control converted to the dominant faith, maybe there languages adopting latin alphabet? Maybe this happens by late 16th/early 17th centuries.
According to Prof. Andrew Wilson's excellent book, The Ukrainians: Unexpected Nation?, one of the strengths of the Ruś Church (that is, the Orthodox Church in Kievan Ruś itself) according to the Ukrainian historiographical tradition was that despite its Orthodoxy, it was fluid enough to accommodate influence outside of the Orthodox tradition (therefore, to Ukrainian historians, the Nikonian reforms in the Russian Orthodox Church, while often billed as bringing the ROC in line with Greek Orthodox practice, was in reality an attempt to bring into the ROC a "Ukrainianized" Greek Orthodoxy). Of course, there's two traditions here of Eastern Christianity, as already been observed:
In theory Belarus and Ukraine WERE mostly Catholic by late 18th century (Byzantine Rite Catholic), of course Union of Brest was hardly noticed by Ruthenian peasants (they were not aware that they suddenly became Catholic) but same thing happened in Prussia, when peasants without even noticing it switched from Catholicism to Lutheranism. In Austrian Galizia, when Union was not delegalised, vast majority of Ukrainians remained Byzantine Rite Catholic, same would happen if Ukraine remained part of PLC.
“The union was not accepted by all the members of the Ruthenian Orthodox Church in these lands, and marked the creation of Greek Catholic Church and separate eparchies that continued to stay Orthodox among which were Lviv eparchy, Peremyshel eparchy, Mukachevo eparchy and Lutsk eparchy that at first accepted the union but later oscillated back and forth.” It seems that by mid-XVII at least Eastern Ukraine was predominantly Orthodox (hence appeal to Moscow during Khmelnitsky Uprising) and even in the mid-XVIII the Orthodox had been prevailing at least in some areas of Right Bank Ukraine and Belorussia.
My own idea would be simple, and within that tradition mentioned above:
>At an early enough stage during the disintegration of Kievan Ruś, keep the notion in what is now Bielaruś (Belarus) and Ukraine going that they are an inheritor of the Ruśian tradition (even with Muscovy doing its thing) and thus they are part of a Ruthene (Русины, Rusynŷ) narod. This means that, unlike OTL, the Ruthenians (what we now call Belarusians, Ukrainians, and Rusyns) must either avoid Polonization altogether or only allow a limited form of it, and some of its traditional institutions from the Grand Duchy of Lithuania (such as the use of the Правда Русьская/Pravda Ruśskaja law code, for example) must be maintained.
>The Common East Slavic written tradition known as Chancery Slavonic or Old Ruthenian must be maintained as the written language of the Ruthenian people, which would mean a continued use of Cyrillic. Now, there could be a possibility of fusing the chancery language (which was in large part based on the speech of Vilnius/Viľńa) with the popular speech, making it seem to us like a hybrid of the other East Slavic languages apart from Russian, with the adaption of Church Slavonic terminology (as the "high" language at the time) and some Polish elements, and that would be left for historical linguistics to figure that one out. Latin script would thus be accorded a secondary status, at first, and eventually take on an appearance (with some exceptions) that approximates OTL Czech and Slovak orthography. Even if Latin script use becomes more widespread, the Cyrillic script would still be seen as their script by which the language is written, especially for religious purposes.
>If Catholic, then among the Ruthenes will still be in the Byzantine Greek Catholic tradition; they can't be pushed into the Roman Rite tradition because then that would make them cling more to Orthodoxy. Rather, I'd see it more as a fluid type thing, with Greek Catholic and Greek Orthodox in a manner similar to the ROC's Nikonian/Old Believer split - that's bound to happen here anyway. The Union of Brest would remain important here for the development of the Ruthenian Greek Catholic Church, but I would argue that the Ruthenian Church here would also appeal to Laetentur Caeli as their method of accepting union with Rome while maintaining autonomy. At the same time, those Ruthenians who wish to maintain Orthodoxy will probably need to learn from the Reformation the need to ensure a renewal of liturgical practice and a need for theologically-sound trained clergy - hence the Mohyla Academy needs to be a permanent phenomenon that is spread throughout the Ruthenian Orthodox Church.
 
Top