What would the effects of Protestantism (specifically Lutheranism) be if it were to fused with or forced upon either say the Greek Orthodox and/or Slavic Orthodox Churches?
I ask because in the TL I'm current working on basically Lutheran Monarchs are placed (or will be placed) on the thrones of various Orthodox countries. This led me to the idea they either over time or at the decree of a Monarchy a fusion of Orthodoxy and Protestantism may arise.
Martin Luther, along with other early reformers, actually appealed to the Orthodox churches for protection and legitimacy again Rome. In some ways Luther would have meshed well doctrinally with Orthodoxy: he maintained some Marian veneration and even celebrated the Assumption, which the Orthodox churches celebrate as the Dormition feast. On the other hand, Luther rejected the Canon of the Mass, the idea of Mass as a literal sacrifice for propitiation, and transubstantiation. While the Orthodox have a different view on how the Eucharist is confected, they also believe that Jesus is physically and totally present in the Body and Blood, something Luther also eventually rejected in favor of a consubstantial union (i.e. the bread and wine remain bread and wine but also become the Body and Blood.)
Catherine the Great was reared as a German Lutheran -- it might be interesting to see the way in which she reconciled her previous Lutheran faith with her participation in Russian Orthodoxy. I'm not sure, but I think she westernized the Russian liturgy to some degree, or perhaps that was Peter the Great.
In sum I would find a fusion of Lutheranism and Orthodoxy difficult, given that even the most "liturgically Catholic" of Lutheran churches (like the Swedes and Finns) greatly de-emphasized the veneration of saints and Mary as compared to pre-Reformation standards. In contrast, the Orthodox have an intense love of Marian veneration, even more than the Roman Catholics in my opinion. I also don't think that the Orthodox would also take kindly to a change in their Eucharistic theology to consubstantiation -- such a change, even if forced, would likely be charged immediately as heresy. I think that the most feasible and peaceful way for a Lutheran to control an Orthodox realm would be to tolerate both a Lutheran synod and an eparchy, even if the Orthodox are slightly disadvantaged by not participating in the aristocratic life of the state. At least the common people could continue to hear their Orthodox liturgy, and remain at peace with the civil authorities.
Prussian Rationalism of the late 18th and early 19th centuries provide a challenging view of what happens when rulers try to centrally plan theology and liturgy. Prussian rationalism destroyed much of the high church liturgy and Latin language influence of the German Lutheran church, as well as some aspects of orthodox Lutheran doctrine. The Prussian kings were Calvinist rulers of a Lutheran people. Their decision to partially Calvinize the Lutherans eventually "worked", but by force. The legacy lives on today -- most of the EKD churches are joint Calvinist-Lutheran churches, but this forced merger was a marriage of convenience that has caused a lot of theological incompatibilities even to the present day.
