The presence of Christianity in Iran goes back to the early periods of Christian history, although scholars do not know when exactly it first arrived. What we do know, is that Christianity was present in northern Mesopotamia (today’s North-Iraq, which belonged to the Sassanid Empire) in the (late) second and early third century, and that the Armenian people, to the north of what is now Iran and then mostly a buffer state between the Roman and Persian empires, converted to Christianity in the early fourth century, before Constantine’s adoption of Christianity in 312.
East Syriac Christianity, often but historically imprecise indicated as ‘Nestorian’ and today preferring the epithet ‘Assyrian’, over the course of the third to seventh centuries spread through most of the provinces of the Sassanid Empire, to the south and to the east into Central Asia, in the early seventh century reaching as far as China. Though Christians never formed the majority of the population (except perhaps in a few specific locations, such as parts of northern Mesopotamia or among certain tribes in Central Asia), their presence in large parts of Persia and Central Asia made them into an important component of local societies. The rise of Islam in the seventh century did not significantly change this. It was only the conversions of Mongol rulers to Islam in the early thirteenth century, followed by the devastating campaigns of Timur Leng in combination with natural disasters such as the plague and climatic changes in the fourteenth and early fifteenth centuries, that ended this church’s widespread presence in the region. In the early sixteenth century, the Church of the East found itself concentrated in what were to become the eastern provinces of the Ottoman Empire (Eastern Anatolia, north Iraq and the Hakkari mountains) and the Azerbaijan region of the Safavid empire, mostly in the Urmia and Salmas plains, west of Lake Urmia. Far away from the rising centers of power (Tabriz, Isfahan, Tehran), these Christians lived simple and mostly isolated lives.
Armenians were present in small numbers in both pre-Islamic and Islamic Persia but were mostly concentrated in the upper north of the country, in Julfa, close to what is today the border between Iran and Azerbaijan. In the Safavid period (1501-1736) they became a more important factor in central Persia, after in 1606 Shah Abbas I forced a considerable part of the community to settle in Isfahan, then the capital of the state. In so-called ‘New-Julfa’ the Armenians became a mercantile and artisanal stronghold in support of the Safavids. In fact, they forged this new satellite city into the center of a worldwide commercial and cultural network that spanned the globe and included Amsterdam, Venice and Madras (India) whose Armenian churches until today can be admired. This network was also used to foster religious and secular learning, especially via the printing of books (after long periods of exquisite manuscript writing). Isfahan in that period also attracted many westerners, and among them were also Dominican and Augustinian missionaries, further acquainting Persians and Armenians with Western learning and western religious forms. Also among the Church of the East in the northwest, mostly in the Salmas plain, Catholic influence started to change local Christian society.
The nineteenth and twentieth centuries brought great changes. The first and most important was the ensuing cultural and religious exchange with Western churches via Protestant, Catholic and Orthodox missions. These missions not only succeeded in the creation of usually fairly small new churches in addition to the older ones, but also, especially for the Church of the East, inaugurated a fast-paced modernization process in which a once isolated community was propelled quickly back into the cultural, religious and political currents of the day. Perhaps the most significant development was that of a renewed understanding of communal identity, from a primarily religious group to that of a ‘national’, ‘ethnic’ community; thus, a form of communal identity that was to transcend the denominational differences that had arisen. Early in the twentieth century, the name ‘Assyrian’, inspired by the excavations near Mosul and referring back to previous usages of the term among members of the church, started to be used for the community as a whole. Among Armenians, similar developments had already started earlier, and in the late nineteenth century many had become active Armenian nationalists, some of whom envisaged the recreation of a separate Armenian state.
The First World War mostly affected the Christians of northwest Iran, first by the refugees who were pouring in after the genocide in Eastern Anatolia in 1915, then in 1918 by local attacks upon Christians who earlier had been protected by the presence of Russian troops (who left the region in the autumn of 1917, after the Russian revolution). Many ended up as refugees themselves, mostly in the southern Soviet states Georgia and Armenia. Others returned to Urmia after the war. The city of Urmia, which in the course of the nineteenth century had become a center of Assyrian Christianity, became a regional center with flourishing Christian churches. Armenians were stronger in Khosrowa and Khoy, and of course, in Isfahan and Tehran, where they started to settle after the Qajar dynasty made it its capital in 1789. More generally, growing social and economic opportunities in the cities on the one hand, and pressure on rural communities from new Kurdish and Azeri Turkish settlers on the other, accelerated a process of urbanization which over the course of the twentieth century led to a Christian population that was almost 100% urban. Additionally, Assyrian and Armenian Christians moved to the oil cities in the south, especially to Ahwaz, where they built new communities.
The late nineteenth and early twentieth centuries also saw the beginning of new Christian communities, made up mostly by converts from Muslim families. The Episcopal (Anglican) Church flourished in various cities, as did various smaller Catholic, Protestant and Evangelical communities that were added to the spectrum of Christian churches over the course of the twentieth century. Overall these groups continued to grow until the Islamic Revolution of 1987. Under the regulations of the Islamic Republic, most older Christian communities are allowed freedom of worship. However, the very strict rules about non-conversion of Muslims and the ensuing practical problems for Muslim-background converts to become an active member of a congregation, in combination with restrictions on Christian presence (of whatever denomination) in the higher echelons of public and state, made life for Christians of all kinds increasingly difficult. Migration of Christians is relatively high, and many communities are struggling to keep their churches going. At the same time there are various reports about increasing numbers of Christian converts in Iran and among Iranians elsewhere. While it is difficult to verify individual reports or the overall numbers involved, there is little reason to doubt the fact that Christianity, despite its decreased visibility in Iranian society, continues to be present in all kinds of surprising ways.