Medieval Armenian historiography mentions a council in the city of Theo­dosiopolis/Garin in the first half of the seventh century (632) with the par­ti­cipation of Emperor Heraclius I (610-641) and the Catholicos of the Armenian Church Ezr I (630-641), where ecclesiastical unity was established between the parties. Ar­me­nian sources, especially from the eighth century, report that the Ca­tho­licos Ezr during this council was deceived by the Greeks and eventually con­verted to Chalcedonism. But so far not a single source is known that reports on the acts of this council.

Despite the fact that acts or other documents from the council of Theo­do­sio­polis have not been preserved, but the acts and documents of ne­go­tiations between the Imperial church and other non-Chalcedonian Oriental churches again for the conclusion of church unity, which took place in parallel, have been preserved. By comparing these documents with information from Ar­me­nian sources, it is pos­sible to restore the content of the document of the council in Theodo­sio­po­lis.

To solve this problem, we divided our study into three parts. In the first part, by studying official documents published by the secular and ecclesiastical leaders of Costantinople and acts of inter-church agreements in the 30s of the seventh century, we show the official christological doctrine of the Eastern Ro­man Empire in the years when the council in Theodosiopolis was held. In the second part, we study the problem of the council of Theodo­sio­po­lis in Armenian and other sources. In the third part, by comparing the information of the Armenian sources with the Syrian sources, we separately studied the issue of the document adopted in the council of Theodo­sio­po­lis.

At the end we concluded that during the council in Theodo­sio­po­lis, the christological doctrine adopted by the Armenian side was not Chal­cedonian, but corresponded to the so-called neo-Chalcedonism or neo-Cyri­lia­nism, according to which „the active subject in Christ is the God-Logos“, and the document presented by Emperor Heraclius to the represen­tatives of the Ar­me­nian Church corresponds to the letter that was addressed to the Patriarch of the West Syrian (Jacobite) Church Athanasios I Gammálā (593/594-630/631) for the conclusion of church unity approximately in 630/31 and was preserved in the Syriac text of the Chronography of Michael the Syrian.