The patriarch nestorien Mar Timothée 1st (728 - 823) is at the origin of a reorganization of structures of the Church nestorienne: it wishes to reinforce the training of the priests and the capacity of the bishops in order to better counter the influence of the Syrian immigrants monophysites and chalcédoniens.

Timothée has, in addition, an excellent scientific and theological formation, as its very many correspondence shows it. Its knowledge of the languages Syriaque, Greek and Arab was worth to him to be solicited by the Caliph Al-Mahdi for its large company of translation of the traditional Arabic Greeks. As a Catholicos, Timothée has its entries with the palate: it is even him which transfer the patriarchal seat of Séleucie-Ctésiphon to Baghdad.