As you may be aware, several Christian churches in Kirkuk, Mosul, Basra, and Baghdad, as well as throughout the rest of Iraq, cancelled their festivities this past Christmas. Ever since the massacre of worshippers in Baghdad’s Church of Our Lady of Salvation last November—followed by attacks on Christian neighborhoods in the city—the Christians of Iraq have been living in a state of unrelieved terror, and they simply do not dare celebrate their faith too openly right now. Moreover, there is no reason to imagine that their situation will become any more tolerable in any conceivable near future.

There are beleaguered Christian communities throughout much of the Muslim world, of course, but it is quite possible that the last remnants of ancient Persian Christianity in Iraq and perhaps Iran will disappear in our lifetimes. If so, and if Persian Christianity is largely reduced to a fragmentary diaspora community, it will mark the end of yet another tragic episode in one of the more extraordinary tales in Christian history—though it is a tale regarding which most Christians know absolutely nothing.

Most of the Christians of Iraq belong to “Assyrian” tradition: the tradition, that is, of the Church of the East (often, and somewhat opprobriously, called the “Nestorian” Church) and of its sixteenth-century offshoot the Chaldean Catholic Church (occasionally, and somewhat opprobriously, called the “Uniate” Chaldean Church). Today, even many Christians who know something of the Eastern churches tend to think of the Assyrian communions as little more than exotic marginal sects; even among the “Oriental” churches (that is, the ancient Eastern communions that did not adopt the Christological formula of Chalcedon in the fifth century) they are often regarded as the least significant.

And yet at one time—from late antiquity right up into the high middle ages—the Church of the East was, in geographic terms, far and away the largest Christian communion in the world, and the most actively evangelical. Had there been such a thing as accurate cartography in the early thirteenth century, any good map of the Christian world might have suggested to a casual observer that European Christianity was little more than a local phenomenon, a sort of provincial annex at the western edge of Assyrian Christendom. Demographically, of course, the balances tipped in the opposite direction. Still, though, the Church of the East was anything but a marginal communion.

The Christianity of all of Syria was from a very early period both an exceedingly scholarly and an exceedingly ascetical tradition. But there was also something of a difference in sensibility between the religious culture to the west, whose intellectual center was Antioch, and that to the East, whose intellectual center was Nisibis. What became the distinct Assyrian tradition, with its distinctive Christological vocabulary, emerged out of the latter. After Nisibis was conquered by Persia in 363, the educated Christians of the city removed to Edessa and other parts of Syria still under Byzantine control; but a little more than a century later, when the Emperor Zeno (d. 491) attempted to impose the Chalcedonian settlement throughout the region, the East Syrian Christian scholars were forced to retreat to Nisibis again, and to the shelter of the Persian Empire, which turned out to be quite tolerant of them.

In 498, the bishop of Seleucia-Ctesiphon assumed the title “Patriarch of the East.” After 553, when the Second Council of Constantinople formally condemned the teachings of Theodore of Mopsuestia (c. 350-429), the Antiochian theologian and biblical exegete whose writings were foundational for East Syrian theology, the Assyrian Church was more or less a theological world all to itself. As it happened, however, this proved to be anything but a historical catastrophe. Pushed out beyond the farthest boundaries of the Byzantine empire, with no hope of reconciliation, the Assyrian Church found itself on the frontier of all of Asia, where no other Christians could even hope to venture.

The Christian scholars of Nisibis and, later, Jundishapur were a disciplined monastic community, devoted to the study of theology and philosophy, as well as to the translation of scripture, Christian literature, and classical Greek texts into Syriac, and renowned for the quality of their medical training. Their zeal for winning converts did not seem to falter before the vast geographical distances or dangerously alien cultures of the Central and East Asia. The Church established itself over time not only in the Mesopotamian region of the Persian Empire, but in eastern Anatolia, Kurdistan, Turkestan, and well beyond. In 635, Patriarch Yashuyab II (d. 643) inaugurated a mission to China that flourished right through the age of the Khans.

East Syrian Christian missions naturally followed the trade routes to the Far East. Merchant caravans from the Arabian Peninsula, India, Central Asia, and China passed through Seleucia-Ctesiphon, and the monks of the Assyrian Church—with their very useful technical, scribal, and medical skills with them—followed in their van, looking for places where their training would make them and the gospel they had to preach welcome. Simply in providing trained physicians and scholars, the East Syrian Church often proved itself an immense benefit to the areas where it settled. Wherever the Church established a new bishopric in its eastward migrations, it built a school, a library, and a hospital. By the late fifth century, the Assyrian mission to Turkestan was under way and would in time reach out to the Mongols. In 781 a Turkish king petitioned Nisibis for a bishop, and soon Episcopal sees were established in Tashkent, Bukhara, and Samarkand. Soon missions were also sent to the Keraits, Uighurs, and other Central Asian tribes.

And then there was China. We know much of the early story of the “Radiant Religion”—that is, Christianity—in China principally from a stone stele dating from 781 and discovered by Jesuit missionaries in Sian-fu in the Shaanxi province in 1625. The T’ang Emperor T’ai-tsung (d. 649) granted an audience to a Persian monk around 638 and was impressed enough (or indifferent enough) to give him permission to preach and found a monastery. For two centuries, the Assyrian mission thrived. Churches and monasteries were established in at least ten provinces.

We know also that the mission suffered a temporary reversal of fortunes in the ninth century, when the Emperor Wu-tsung (d. 846) laicized all the native priests and monks in the kingdom. But there were still monasteries in China in the eleventh century, and around 1095 the Patriarch of the East, Sebaryeshu III, appointed a bishop to the see of Cathay (or Northern China). Even as late as the thirteenth century, when the Radiant Religion enjoyed the favor of the Mongol court of Kublai Khan (1215-1295), Chinese monasteries were still being built. And in 1280, Mark, the Chinese (Uighur) bishop of Cathay became the Syrian Patriarch of the East, under the name Yahbalaha III (d. 1317).

How far the East Syrian missions reached we are never likely to know for certain. The “Thomas Christians” of India were East Syrian in theology, loyalty, and population from an early period, and in the eight and ninth centuries the new immigrants who swelled the numbers of the Malankara Christians of India were definitely East Syrian. As early as the sixth century, Cosmas Indicopleustes encountered East Syrian Christians on the remote island of Socotra in the Indian Ocean, and there are passing references in texts from later centuries to one or another bishop of Socotra. And East Syrian missions definitely penetrated into Tibet before the late eighth century. Some historians even believe there is sufficient textual and physical evidence to suggest that East Syrian Christians reached Sri Lanka, Java, Sumatra, Japan, Korea, Burma, Malaya, Vietnam, and Thailand.

By the end of the middle ages, however, the Assyrian communion had been reduced to a shadow of its former magnificence. There had been some pressure upon the native sees from the time of the Islamic conquest of the Persian Empire, but East Syrian scholars and physicians had for centuries occupied a vital place in the Caliphate. But the greater Assyrian Christian world of Central and East Asia had remained intact and largely unperturbed into the fourteenth century. Of course, the Christians of Central Asia suffered terribly along with everyone else when the horde of Genghis Khan (c. 1150-1227) was destroying every village and city in its path. But the grandsons of Genghis—Möngke (1208-1259), Kublai (1215-1294), and Hulegu (1217-1265)—were for the most part well disposed towards the Assyrian communities. Hulegu even took a Christian wife.

In the late thirteenth century, however, the great reversal began. In Baghdad, Ghazan Khan (r. 1295-1304) adopted Islam, and at once the East Syrian Christian community became the object of ferocious persecutions, including numerous massacres. Then, in 1369, the Ming Dynasty came to power in China and instituted a systematic extermination of foreign creeds. The Assyrian Church had soon disappeared. And in Central Asia the rampages of the Turkic Muslim warlord Timur (1336-1405) left no living traces of East Syrian Christianity in their wake.

And yet, down the centuries the Church of the East has persisted: a small community, perennially persecuted in the place of its birth, and until very recently seemingly indomitable. Far away from there—in India, where it has had a home for centuries, and in North America, where it has had to find a new home in a dark time, and elsewhere—its scattered branches continue to bear fruit, not copiously, perhaps, but indefatigably. But in its homeland it is being pushed towards the edge of extinction.

So it goes, I suppose. History is not at our command, and the future does not lie in our power; we must do what we can, but we can do only so much. And, in the end, all cultures rise and fall; none is eternal. Nevertheless, for anyone who knows the strange, glorious, and too often forgotten history of the Church of the East, it is difficult to view the current situation without a very special and very intense bitterness.

David Bentley Hart is a contributing editor of First Things. His most recent book is Atheist Delusions: The Christian Revolution and Its Fashionable Enemies (Yale University Press). His previous “On the Square” articles can be found here.