I have been interested lately in early papal history, and have been hearing/reading a lot about schisms, over what read to me as resolvable nuances in Christology. Were schisms such as Monophysitism, Nestorianism, and Arianism driven by incompatibility of faith, or did they tend to stand proxy for power struggles between political factions?
I am curious how you think the position of the trinity existing as the immutable nature of God vs a non trinitarian position that elevates the Father to a separate level than the Son, as in the case of Arianism is a "resolvable nuance", but no matter...
There were political dimensions to religion in this time of course, there always have been political dimensions to religious practices, but to dismiss them as entirely politically motivated is a mistake, and in many cases, especially in late Antiquity, the theological debates of the day had an indelible impact on the political realm, but it is difficult, if not impossible, to tell where politics ends and religion begins, or vice versa.
Arianism for example is essentially a debate about the nature of Christ, or the Son, in relationship to God the Father. The orthodox position is that the Son is co-eternal and consubstantial with the Father, and that with the Holy Spirit, form the trinitarian God, but the Arians, or the followers of Arius, argued that the Son had to have been created by the Father and was therefore not coeternal and consubstantial with the Father, and that God was properly understood as the Father, whereas the Son was a divine being but not fully "God".
While a theologically interesting debate, it is not a debate that really had political implications yet.
In 321 the teachings of Arius were condemned as heretical following the Council of Nicea, and the Nicene Creed was formed which is the basis of Church doctrine and belief. The Christological debate was "settled" at least for the mainstream Christian population of the Roman Empire, but the political disputes that started in a debate about the nature of Christ and the Father soon spilled over into new political ones.
Arianism did not disappear following its condemnation at the Council of Nicea, and the Roman Empire continued to feel the effects of what was originally a dispute about Christology for centuries. The Roman Emperor Constantine, while the first pro-Christian emperor, seems to have had a relatively thin interest in the actual theological debates of Christianity, and undertook his efforts such as the Council of Nicea, and other synods and various Church meetings/debates, to smooth over internal political divisions within his empire, rather than out of genuine religious concern. Indeed, if anything, Constantine seems to have been somewhat pro-Arian as he retained Eusebius at his court, a well known pro-Arian bishop, and even received baptism from him on his deathbed.
In the years following Constantine's death, Arianism experienced a broader rebirth across the Roman Empire that wouldn't be stamped out until the late 4th century among the church and political elite of the Roman world. Constantine's imediate successors for example were often pro-Arian in their reign and leanings on the nature of Christ. This only came to an end with the death of figures like Valens and the broader discredit of the Arian figures in the Church as the Nicene Creed and the "orthodox" positions on Christology became the norm across the Empire.
However Ariainsim survived for several more centuries among the "barbarian" peoples of the Germanic kingdoms, and the Goths, Lombards, and Vandals all embraced Arian Christianity as they moved into Roman territory, and trinitarian Christianity took several centuries to work its way into the political realm of these post-Roman kingdoms. While the nature of the Arian church in these states is somewhat obscure, due to the lack of sources, there were clear distinctions and tensions between teh Arian ruliong classes and the orthodox populace at large, this was especially the case in Vandalic Africa. However, due to the ongoing cultural pressure of the larger orthodox population these populations would eventually convert.
This is only one example, and there are of course a plethora of heretical movements that that were spreading in the period of Late Antiqutiy, but I hope that this example at least demonstrates that the line between politics and religion could start off clearly cut, but later devolve into political tension and dispute.
I can answer about the Paulician and Tondrakian heresies in Armenia from the 7th-11th centuries, which are less well-known. The Paulicians are notable for being deported to Thrace and Bulgaria around the 800s in the tens of thousands and many were killed, for two reasons: (1) they were causing problems to the Byzantine Empire as they opposed their power and often even allied with Muslim rulers despite being Christian themselves. (2) Their anti-establishment or anti-imperial designs got them deported to Thrace. In exchange for being allowed to practice their faith, the Byzantines wanted them to defend against Bulgarian forces.
The Paulician heresy was significant because of its stated anti-establishment views. Soviet historiography read them through the lens of class struggle, of the lower working classes rebelling against the ossified structures of power, both of the Armenian Church and then the Byzantine Empire and official church. (Historian Nina Garsoïan agreed that this assertion is supported by both Greek and Armenian sources, but held it only a limited description of the sect.) They fought some battles against the Byzantines, even reaching near Constantinople at one point in battle.
Official historians of that era (8th-11th centuries), especially church clergy, viciously attack the Paulicians and Tondrakians as wicked heretics or gnostics at best. Like Nestorians, they did not venerate Mary. They allegedly held views in line with modern-day Protestants (Edward Gibbon considered them as "worthy precursors of the Reformation"), rejecting the Christian cross, rituals, sacraments, church hierarchy and many of the rituals (like water baptism). Their center of power was in Tephrike, a city just on the frontiers of Armenia, Byzantine empire, and the Arab muslim world.
After they were deported, the Paulicians experienced a revival and in turn ended up largely influencing the later Bogomils, Cathars and so on, which appeared in mainland Europe before the Protestant Reformation.
In addition to the excellent answers you have already received, I would like to add a few words about how it is often very hard to identify which political actors endorsed or rejected any given theological position, and about how it is important to remember that, while to a contemporary eye most of these debates may seem far removed from any practical consequence, they nonetheless had huge effects across all social classes.
This latter observation can be exemplified by the so-called Trishagion riots of around 510. The new emperor, Anastasius, was suspected of myaphysite leanings, that is, he preferred the notion of a united, divine nature in Christ. Things came to a head only when a new doxological formula was introduced in the Mass. People recognised it as a myaphysite rallying cry and in the riots that followed the emperor was forced to flee Constantinople. Eventually Anastasius came out on top, but just two years later, when he had the same formula (called the Trishagion) uttered again from the altar not only new riots broke out and he had to confront the crowds himself in the hippodrome, but he also had to deal with the open revolt of a military officer, the comes Vitalian.Strange as it may seem to us, it was the popular reaction to liturgucal changes that precipitated a political crisis. How to decipher the reaction of a crowd to socio-religious stimuli? Was it simply devotion to the orthodox creed that motivated the riots? Were they fomented by political agents? It is hard to answer questions such as these given the nature of our sources. It seems to me that the emotional element that moved the crowds of Constantinople should not be dismissed out of hand.
In the Latin-speaking west things were, if possible, even more confusing. Marilynn Dunn has written about the complex interaction between the religious macrocosm of the theological debates at the highest level of the ecclesiastical hierarchies and the numerous microcosms of local cultual practices in the Romano-Germanic kingdoms. Barbarian rulers had to balance their religious policies between, on the one hand, the political power wielded by the established church, behind which stood the power of the Roman Empire, and, on the other, the cultual practices that developed among their own people. But the established church was often divided, and, since the most recent theological positions were nearly always debated first in the Greek-speaking East, it was hard work trying to keep up with the news. This had an effect on the various "microcosms"of local cultual practices: while in surviving texts Latin clerics are eager to condemn heterodox practices and belief as "Arianism" it seems likely that there existed many flavors of heresy in one, including elements that at times had been orthodox and later fallen afoul of the latest theological definitions.
To give you an idea of this confusing situation, I will presnt you with a known western reaction to the Trishagion crisis that I have described above. Avitus, bishop of Vienne, now in France, had a complicated relationship with Gundobad, king of the Burgundians. Notionally, Gundobad was an Arian but he had no problem acting as Avitus patron and asking him for advice. When news of the Trishagion riots reached Burgundy, Gundobad (understandably) looked for help in trying to make sense of the various theological positions and he reached out to Avitus. In doing this, Gundobad's main preoccupation was likely a political one, that is, he wanted to maintain good relations with the Empire. Unfortunately for him, Avitus was utterly lost. A surviving letter of his completely misrepresents the situation, depicting Anastasius as orthdox and the Trishagion as the correct formula. To put it simply, the distance and the lack of direct communication with the people actively engaging in these debates were unsormountable obstacles for the times. Were there political aspects in Avitus theological speculations? Possibly yes, but how are we to understand them when we know for a fact that he was writing on the basis of incomplete and incorrect information? It is easy to construct grand narratives around secular policies masquerading as religious dogma but such narratives seldom take into account the messy state not only of our sources but also of the way in which such sources were composed
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