Christianity in Persia traces its roots to the Apostolic age, with Sts. Thomas and Bartholomew allegedly transversing the Parthian Empire. The churches that they established would be collected as a federation under the Sassanian Empire, and establish the traditions of the 'Church of the East'. Many of these documents relate to the earliest period of the church under Sassanian rule, prior to the Arab conquest.
Ethiopia claims to be the second oldest Christian name in the world, with only Armenia being senior. Christianity was brought to it by the Syriac sage, St. Frumentius in the 4th century, which was quickly adopted by the court of the kings of Axum. The Monastic life of the Ethiopian church produced and maintained a number of texts which are found no where else in Christianity, particular in its extended Biblical canon.
It remains a mystery to when Christianity came to Arabia. St. Thomas was said to have been shipwrecked in Socotra, and St. Paul is known to have spent time (likely in the Hellenized city of Petra). However, there were thriving Arab Christian communites in Najran, Mecca, and Petra, where some documents have survived to the present day. Moreover, there is also a long tradition of Catholic Christianity in the Maronite community in Lebanon.
Christianity was brought to Nubia was either St. Matthew or St. Mathias in the first century AD. It florished in communion with the neighboring Coptic and Ethiopian churches for centuries, before being crushed under the weight of the Ottoman invasion in the 16th century. There are only a handful of texts that have survived and many of them are fragmentary. However, Christian Nubia held notoriety for its piety and the zeal of its denizens.
The Byzantine tradition is the tradition of Christianity that is found specifically in the Eastern Roman Empire, and partially in its broader cultural commonwealth. While various regional influences impacted the church in Asia Minor, the intellectual heavy weight of Byzantine religious thought and culture was Constantinople, with its Imperial court and university (the oldest in the world). The Byzantine church's texts have been well preserved and well propagated by Greek, Latin, and Russian scholars who has sought to preserve the traditions of the 'Christian Empire'.
The church in Egypt has roots even during the lifetime of Christ. Egyptian Christians venerate the sojourn of Christ and his family in Egypt when he was in exile hiding from Herod the Great. The Coptic church, headquartered in Alexandria has maintained vast monastic libraries and has acted as the great custodian of Christian history, despite their heavy centuries old persecution. The language of the Coptic church was maintained specifically by the church through the medieval period and well into the 16th century, before becoming exclusively liturgical.
Christianity was brought to Armenia in the 1st century AD the apostle St. Bartholomew who established much of the earliest bishoprics in the nation. Armenia also hold the supreme dignity of being the first Christian nation in the world, converting in 301 AD. Because of its antiquity and its partial isolation from the rest of Christianity, the traditions and texts of the Armenian church developed independently, and much of the oldest traditions of Christendom have been preserved in the various monastery library of the Caucus mountains.
The Syriac church is definitely linked to its sister churches in Armenia, Persia, and India. Syriac Christian continue to worship and write in the ancient tongue of the Syriac peoples, a tongue which Christ himself spoke in his own lifetime. This tradition is partially split between East Syriac texts, which were largely a function of the Church of the East, and the West Syriac texts, which are more familiar to Catholic and Orthodox audiences. Today, the light of the Syriac tradition is carried by the Assyrian and Chaldean communities in Iraq, Turkey, Syria, and abroad.
.While the apostle, St. Thomas, came to India in the first century, there are a limited number of documents that has survived from the ancient church in India. Many of the church's oldest traditions are preserved in native folk songs of Kerala. The Indian church maintains many of its ancient traditions, including the use of the Syriac language, which it employs in its liturgy
Christianity is said to have come to Iberia (Georgia) during the first century through the work of St. Andrew the apostle. During its existence it has held close ties with both its neighboring Armenian Apostolic church, but also by Byzantine influence. The Georgian tradition of Christianity has come down to our present age as the Georgian Orthodox Church.
The coming of the Slavic peoples in the 6th century caught much of the Eastern church by surprise. There was a question of how these different groups should be evangelized and under who's authority they should be. For Western Slavic groups (Poles, Slovens, Moravians, Croats, Slovaks, Bohemians, and Silesians) this would eventually means submission to Rome, but with additional license given for their own national identities. Many of their earliest writings reflect this, and the desire to maintain Slavic identity while incorporating it into the Latin church.
The Slavic peoples who lives to the East and South found themselves drawn to the Imperial center at Constantinople, and became incorporated into the greater Byzantine commonwealth. For these groups (Bulgarians, Serbs, Wallachians, Moldavians, Macedonians, Rusyns, Russians, Ukrainians and Belarusians), emulating the their historic ties to Constantinople was important, and demonstrating the continuity of their traditions with Byzantine was a major function of their hagiographical and ecclesial texts.