The “Apostolic Church of the East” is, in the West, the least-known church of Christendom and is currently the smallest of the Eastern churches.
Until the present day, little consideration was shown in church history and theology for the fact that early Christianity spread not only within the Roman empire – i.e. Europe and the Mediterranean region – but also beyond the imperial boundaries. Already in the ﬁrst century there were Christian communities in Mesopotamia, which was part of the empire of the Parthians, superseded by the Persian Sassanians in the third century. As early as the ﬁfth century the Oxus had been crossed, and Sogdians and Turks, as well as the South Indian Malabar coast, had been reached. East Syriac Christianity gained a foothold on the Arabian Peninsula and, in the seventh century, reached the Chinese imperial court of the Tang Dynasty. In the eleventh century, those Turkish-Tartar tribes in Central Asia which eventually formed part of the Mongol kingdom were won, entirely or in part, for Christianity. Thus the “Church of the East” achieved the greatest geographical scope of any Christian church until the Middle Ages. For reasons of historical and political circumstance, the church has become a minority today and is represented in the countries of Iraq, Iran, and India, as well as in the diaspora in North America, Australia, Syria, the Caucasus, and Lebanon. The Apostolic Church of the East has preserved an important heritage of theology, history, and spirituality, which has
been rejected as heretical – “Nestorian” – by the rest of Christendom.