It will always be difficult to form a clear picture of the initial stages of a religion, however, much one may know of the revolutionary character of the founder's circumstances and basic religion. It is quite a long process for a new religious society to free itself of the old traditions, to create its own image and to justify its claim to independence. Christianity is no exception in this respect. To the Romans, for example (cf. Suetonius and Tacitus), it was scarcely more than an episode in the history of Jewry, an internal Jewish problem giving rise to disturbances which had regrettable political consequences for the Romans. Nevertheless, the young Christianity very soon became a missionary church whose history is recorded in the Acts of the Apostles. It is clear that this missionary work soon made a lasting mark. As early as the beginning of the 2nd century, the Younger Pliny, the imperial representative in the province of Bithynia et Pontus in Asia Minor, found it necessary to write (x. 96) to Trajan for advice concerning the treatment of the Christians. At about the same time, Tacitus (Annals xv.44) records that the "pernicious superstition" (exitiabilis superstitio) had spread to Rome itself (per Urbem). One should be cautious, however, in assessing the extent and influence of these first communities, and even more so in evaluating the missionary activities in the Euphrates-Tigris area. It is only necessary to establish that Christian groups existed in these parts of the empire at an early date.

The first opportunity for people of Iranian origin to learn of the new teaching was provided, according to Acts 2.9, by the pentecostal miracle in Jerusalem (Aelia Capitolina), which was witnessed by Jews from Parthia, Media, Elam, and Mesopotamia. This statement, although we may interpret it with every reservation, clearly indicates that the starting point of Christianization was the Jewish-Christian groups to the east of the Euphrates. These groups were constantly used as a plaything between Roman and Parthian interests. Their early strength was concentrated in the district of Adiabene (main town, Irbil; Gk. Arbela) and in the district of Osrhoene (main town, Edessa; Gk. Urrhai). Missionary activity was anonymous and took the form of a slow but increasing infiltration. This however, was not so notable as to interest the non-Christian historiographers of the day. It is now generally assumed that Adiabene was the actual center, even more important than Edessa; this importance was largely due to the prominence of the Jewish element in the district, and the conversion of the ruling, Parthian-oriented dynasty to Judaism in the 1st century AD under Queen Helena. From AD 109 to 116, her grandson, Abgar VII, was king of Osrhoene, which, for a short period in the middle of the 1st century, was under the control of Adiabene. According to the Syriac "Chronicle of Arbela", written by the otherwise unknown Mesiha-Zeka in the 6th century, Christianity in Adiabene stands out clearly from its surroundings as early as the year 100, when Mar Peqida was appointed bishop by his teacher, Addai, by the laying on of hands. It is remarkable and certainly in accordance with the actual circumstances that the bishops succeeding Peqida bear distinctly Jewish names (Semson, Ishaq, Abraham, Noh, Habel [Abel] etc.). At the time of the Iranian change of dynasty at the beginning of the 3rd century there were, according to the "Chronicle", more than twenty bishops from Bet Zabdai northwards through Karka de Bet Selok and southwards to Susiania (Bet Lapat, Hormizd-Ardashir) and Mesene (Perat de Maisan), but none in Nisibis or Seleucia-Ctesiphon.

-The Cambridge History of Iran, vol. 3(2): The Seleucid, Parthian, and Sasanian Periods, ed. Ehsan Yarshater (NY: Cambridge UP, 1983), 925.