Under Bahram I and the influential priest Kartir, imperial policy shifts decisively against Manichaeism: Mani is imprisoned and executed (traditionally dated to 274). This marks a major moment in which Zoroastrian clerical influence helps define state boundaries of acceptable religion.
Kartir’s Middle Persian inscription (composed during Bahram II’s reign, often dated to around 280) claims state-backed advancement of the Mazdayasnian religion and the suppression of multiple religious communities (including Jews, Christians, Buddhists, and Manichaeans). The text is a key primary witness to late-3rd-century clerical power and coercive religious policy rhetoric.
During renewed war with Rome, Shapur II adopts a harsh policy toward Christians in the empire, viewing them as politically suspect amid Roman Christianization. Later Christian tradition remembers this as a prolonged “Great Persecution,” illustrating how interstate conflict could intensify confessional policing under a Zoroastrian state framework.
Yazdegerd I permits Christians to worship openly and rebuild churches (commonly dated to 409), reflecting a pragmatic turn toward integrating minorities and easing tensions with the Roman Empire. The policy underscores that Sasanian religious governance could alternate between coercion and managed toleration.
Convened in the imperial capital in 410 under Yazdegerd I, this synod structured the Christians of the Sasanian Empire into an officially organized hierarchy centered on Seleucia-Ctesiphon. It exemplifies Sasanian policy of administratively incorporating minorities while retaining Zoroastrianism as the state religion.
After incidents involving attacks on Zoroastrian fire temples and subsequent state reprisals, Bahram V’s persecution of Christians contributes to the Roman–Sasanian War of 421–422. The episode shows how protecting Zoroastrian sacred institutions could become a casus belli shaping broader imperial policy.
In 424, under Catholicos Dadishoʿ, the Church of the East declares that its leadership will not be judged by western (Roman/Byzantine) ecclesiastical authorities. This move had a strong political dimension: distancing Persian Christians from Roman church control reduced suspicions of divided loyalty under Zoroastrian imperial rule.
In 445–446, sources report new restrictions against Christians in the Sasanian Empire (including expulsion from the army) alongside intensified promotion of Zoroastrianism. Yazdegerd II’s policies are often interpreted as targeting non-Zoroastrian elites to enforce obedience during political and military strains.
A sixth-century Syriac text (History of Karka) centers on violence in 446 in the Kirkuk region (Karka de Beth Selok) under Yazdegerd II, linking persecution to demands for participation in state religious observances. The account highlights tensions where Zoroastrian civic-ritual expectations conflicted with Christian prohibitions.
The 484 synod at Gundeshapur (Beth Lapat) reflects internal consolidation of the Church of the East inside the Sasanian Empire; later sources associate it with endorsement of Theodore of Mopsuestia’s theology. It illustrates how minority communities negotiated identity and leadership structures under a Zoroastrian imperial order.
Kavad I’s reign (488–531) is associated with the rise of Mazdak and a reformist movement that threatened established aristocratic and Zoroastrian clerical interests. The crisis demonstrates that Sasanian religious policy also had an internal political-economy dimension, not only a minority-management function.
Under Khosrow I, the Mazdakite movement is violently suppressed (often placed around the transition from Kavad’s death in 531 into Khosrow’s early reign). The purge reinforced the alliance between monarchy and Zoroastrian establishment, reasserting the role of orthodox clerical authority in state order.
Hormizd IV is portrayed in several traditions as refusing Zoroastrian clerical demands to attack Christians, emphasizing the crown’s capacity to check priestly influence when politically advantageous. This moment illustrates that Sasanian “state religion” did not imply uniform policy, but ongoing negotiation between king, clergy, and minority elites.
During Khosrow II’s reign, court politics and factional Christian rivalries shape religious policy; sources report he favored Miaphysites and sought to impose their position, reflecting a shift from earlier patterns of simply policing non-Zoroastrians. The episode underscores the complexity of Sasanian governance over multiple confessional communities.
The Rashidun victory at al-Qadisiyyah (16–19 November 636) initiates the rapid loss of Iraq and the Sasanian capital region, undermining the imperial institutions that had sustained Zoroastrian clerical authority and Sasanian religious policy. This military turning point precedes the broader political collapse completed later in the 7th century.
Ardashir I overthrows the Arsacid (Parthian) dynasty and establishes the Sasanian monarchy. Early Sasanian kings promoted Mazdayasna (Zoroastrianism) as a pillar of royal legitimacy, setting the stage for later, more institutionalized priestly power and state religious policy.
Zoroastrian Church and Religious Policy under the Sasanians (3rd–7th centuries)
