From “History of the Apostolic Church” by Afshin Khorrami
In the centuries between the conquests of Vaballathus and the conquests of Abu Yusuf, the Palmyrene and Sassanid Empires emerged as the premier powers in Western Asia. In Persia, imperial ideology claimed that the power of the Sassanid Shahs derived from god, and that they had a sacred duty to support the Apostolic Church. Shapur’s conversion to and patronage of Christianity led to the weakening of the Parthian nobility that had previously dominated Persia, leading to the centralization of the Persian state apparatus into the hands of the Shah[1]. The Sassanid Shahs empowered the Church at the expense of the nobility, to the point when the novility were effectively irrelevant. Each Sassanid satrapy was administered by a Bishop and run by a bureaucracy consisting of priests. With this strengthening of the Church, the Patriarch Ctesiphon grew to enjoy a position of power and influence rivaled only by the Shah himself.
Later into the Sassanid state’s existence, the Patriarch and the Shah would come into conflict over whose influence was greater[2]. The Patriarchs were able to gain the upper hand by using the devout Persian peasantry to their advantage. If ever a Shah went against the wishes of the Patriarch, than the Patriarch would simply excommunicate him and the peasants would revolt to put a loyal Shah on the throne. Thus, the institution of the Shah was effectively reduced to a puppet of that of the Patriarch. While the Patriarch had effectively seized absolute power over the institutions of government, the Shah was still the military leader of the Persians. Beneath the Shahanshah were the spahbeds of the various branches of the Persian military, those being the aswaran[3], the elephant corps, the immortals[4], the army, the navy[5], and the Daylamites[6].
In the Palmyrene Empire, a similar system of theocracy developed, only this time with the Emperor at its center. Palmyra’s first ruling dynasty, consisting of Odaenathus, Zenobia, and Vaballathus, all claimed to be living gods. While the Emesene dynasty that replaced them had no such pretensions, their entire claim to legitimacy was based around being priest kings who would rule on behalf of and worship Palmyra’s founding dynasty. While the city of Palmyra stopped being an administrative capital after the Persians sacked it one to many times(being replaced with the strategically-placed city of Byzantion), it continued to serve as a ceremonial capital where the Emperor would perform elaborate sacrifices of bulls to the god Mithras(and by extension, Odaenathus), his wife Isis(and by extension, Zenobia), their son Vaballathus, Alexander of Macedon(whom Odaenathus was the reincarnation of), and the Ptolemaic Queen Cleopatra(whom Zenobia was the reincarnation of). This festival of the Tauroctony was central to the Palmyrene state and the Palmyrene identity, so much that the loss of Palmyra would mean the eventual overthrow of the Emesene dynasty.
Three philosophical schools would become predominate under the Palmyrene Empire; Mithraism, Platonism[7], and Stoicism. Mithraism is centered around the worship of the god Mithras. In Mithraism, Mithras created the world by slaying the primordial bull, and is traditionally paired with the goddess Isis. Mithraists worship in underground temples called mithraea. Members of a mithraeum progress through various ranks. With each passing rank, more hidden knowledge is gained. Traditionally, only men were allowed to join the mithraea, while the women and children worshipped Isis in similar secret meeting places. The second major school, Platonism, is derived from the teachings of the Greek philosophers Socrates, Plato, and Aristotle. Platonism provided the basis of the ideal ruler in Mithraic civilization, the philosopher-king, as well as the typical social structure of Mithraic Europe. Several key concepts that entered Mithraism, such as emanations and reincarnation, are rooted in Platonism.
The third major philosophy was Stoicism. While Mithraism focuses on the metaphysical nature of the universe and Platonism focuses on social structures and ideals(including the ideal ruler) with a mystical structure based on those ideas, Stoicism emphasized living according to virtue and accepting the will of the gods, and provided the moral framework for Mithraic civilization[8]. In addition, an unofficial fourth philosophy also developed in the form of Hellenism, a collection of pre-Mithraic pagan traditions that were still widely believed by the lower classes. Among the Germanic peoples of Northern Europe and Vinland, Hellenism is replaced with the local folk religion of Asatru, and among the Mithraic Slavs with Rodnovery, but this basic of Mithraism, Platonism, Stoicism, and a local folk religion exists throughout Mithraic Europe. These philosophies are not strictly “religions” in the Abrahamic sense of the word in the sense that they aren’t viewed as something you are but rather something you do, it is perfectly acceptable to be a Mithraist, a Platonist, and a Stoic all at the same time. Palmyra also had a large Ebionite Christian minority, and tolerated Jews and Zoroastrians(especially since Zoroastrian Armenia was a key Palmyrene ally).
The Persians and Palmyrenes, nicknamed “the two eyes of the world” by the esteemed Persian poet Shapur Yosefzadeh, were rivals for regional hegemony and fought many wars. These wars were ideological in nature, as the Persians wished to reunify the empire of Cyrus the Great and the Palmyrenes that of Alexander the Accursed.The largest of the wars between the Palmyrenes and Sassanids before the one that would ultimately bring about the end of both empires began in 535 when the Palmyrene Emperor Mithradotus II launched a surprise invasion of Persia. He was able to take the city of Ctesiphon, only for Shahanshah Ardashir II and Patriarch John IV to reestablish themselves at Gundeshapur, from where Ardashir would launch a successful counter-invasion of the occupied territories, after which the Shah and Patriarch would return to Ctesiphon and Mithradotus would sign a treaty of “eternal peace” with the Persians before being overthrown by his brother, Emperor Odaenathus VII. Ardashir would be given the title “Anushirvan”, or “immortal soul[9]”, and would later be canonized as a saint[10]. The next major war between the two would lead to the weakening of both empires before the Arabs of Abu Yusuf.
From “The Life of Abu Yusuf” by Abdullah Al-Yathribi
After having secured himself as the successor to Jabalah and the inheritor of his kingdom, Abu Yusuf set his eyes toward the Lakhmid Kingdom. Abu Yusuf was easily able to conquer the Lakhmids, but with the Banu Lakhm gone, a new enemy emerged to challenge him. The Sassanid Persians had traditionally relied on the Lakhmid Kingdom as a buffer against the nomadic Bedouin tribes from further in Arabia. Fearing that Persia was now in a vulnerable position, Shahanshah Yazdegerd IV[11] launched a preemptive invasion of Arabia. While Yazdegerd and his forces were bogged down in the desert, Abu Yusuf and his armies crossed the border into Persian Mesopotamia.
With Ctesiphon threatened, Yazdegerd was forced to abandon Arabia and face Abu Yusuf in Mesopotamia. The two met at Babylon[12], where Abu Yusuf would capture Yazdegerd and hold him hostage. He then set his armies towards Ctesiphon, and captured the city. As with during the Palmyrene Emperor Mithradotus’ capture of the city a century earlier, the Patriarch fled to Gundeshapur, and Yazdegerd’s cousin Yonetan II was crowned as the new Shahanshah. Abu Yusuf then set out towards Gundeshapur. Abu Yusuf’s forces captured the city, alongside the Patriarch and the Shah. Yonetan was executed, and Abu Yusuf was declared the new Shahanshah of Persia. Abu Yusuf was tempted to execute the Patriarch as well, but a Persian advisor by the name of Khosrau convinced him to spare the head of the Apostolic Church, saying that he “could make the people of Persia and enemy of Arabia until the Day of Judgement, or the the loyal subjects of the Arab king.”
From “Dar Al-Yasu[13] by Yoseph Qatraye
After conquering Persia, Abu Yusuf had no more major conquests. He wished to conquer the Himyarite Kingdom, but by this point he was an old man, and the conquest and pacification of Persia had significantly aged him. While the Sassanid Empire fell with the capture of Gundeshapur, Abu Yusuf would spend the next eight years of his life pacifying various parts of Persia that refused still to accept Ebionite Arab rule. Some mountainous regions of Persia would not be fully incorporated into the Arab Empire until after Abu Yusuf’s death. After Persia had fallen, Abu Yusuf would return to his capital of Damascus and live there for the rest of his life. His one last major achievement was creating the Qanun, the legal code of the Arab Empire based on the Law of Moses lashed out in Leviticus and combined with the tribal laws of the Bedouins. Abu Yusuf would die of old age in his palace at Damascus at seventy nine years old. In the span of his lifetime, he had gone from a random tribesman in the middle of the desert, seen as a barbarian by more important peoples, to the undisputed master of Western Asia, seen as a king, a conqueror, and a lawgiver. But despite all of Abu Yusuf’s achievements, none of that mattered anymore. Now all that mattered was succession to the empire he had conquered.
[1]Sassanid Persia IOTL was essentially feudal, with powerful families such as the Seven Great Houses(the Houses of Karen, Varaz, Ispahbudhan, Mihran, Suren, Zik, and Spandiyadh) having considerable influence. TTL’s Sassanid Persia is instead an absolutist monarchy with a centralized bureaucracy, roughly comparable to Bourbon France or Imperial China IOTL
[2]The OTL debate between the Pope and the Holy Roman Emperor over the appointment of bishops happens between between the Patriarch and Shah ITTL. Just as the Catholic Church IOTL modeled its structure off of the Roman administrative system, so too does the Apostolic Church model its administrative structure off of that of Persia. Beneath the Patriarch, each satrapy has its own bishop who serves as satrap(to the point that the two positions become one and the same), with priests below him who serve as government bureaucrats in addition to their clerical roles, and then monks who don’t really play any formal role in the government but are valued for their advise. Since the Apostolic Church effectively is the government bureaucracy, the Patriarch is able to set himself up as the de facto ruler of Persia. A system sort of similar to the Shogunate in OTL Japan emerges, with the Patriarch playing the role of the shogun and the Shah playing the role of the emperor.
[3]Cataphracts
[4]An elite cavalry division consisting of 10,000 men, intended as a revival of the similarly named branch of the Achaemenid military
[5]The Sassanids weren’t much of a naval power ITTL or IOTL, but had one nevertheless(almost entirely used against the Palmyrenes, since a navy’s pretty useless against Göktürks or Hephtalites)
[6]Elite infantry from Daylam, a mountainous region of Iran inhabited by a semi-barbaric people who gave their name to the Daylamite branch of the Sassanid military.
[7]We would call it “Neoplatonism”, but this is a modern name for it and people at the time would’ve simply called it “Platonism”, so I will as well
[8]The best comparison for this IOTL is China. Think of Mithraism as Buddhism, Neoplatonism as Confucianism, and Stoicism as Daoism.
[9]This same title was given to Khosrau I IOTL
[10]The Apostolic Church acknowledges the existence of saints, but doesn’t believe that they can be prayed to and regards the concept of patron saints as polytheistic. Sainthood in the Apostolic Church is simply a recognition of either being one of Jesus’ Apostoles, being a former Patriarch of Ctesiphon(all Patriarchs are canonized upon death), having some sort of miracle attributed to you, or(in Ardashir’s case) extraordinary deeds in service of your faith. All Apostolic saints are given the Aramaic honorific “Mar”, meaning “lord”.
[11]The previous Shah, Ardashir III, had been deposed after his failure against Palmyra
[12]By this point, Babylon has largely been overshadowed by Ctesiphon, but it has retained some importance as a major center of learning, with the the Church-run University of Babylon being the most prodigious center of learning in the Sassanid Empire
[13]Arabic for “Realm of Jesus”, a common nickname for Abu Yusuf’s empire