In this work, a concise but comprehensive presentation of the relations between Church and State during the middle Byzantine period from 867 to 1261 AD is attempted. Based on sources, specifically the historians and chronographers of the period under examination, the fluctuations in the relations between the two highest centers of power of the Byzantine state, namely the emperor and the Patriarch, are presented.

This study was prompted by the observation that strong personalities, who ascended either to the imperial or patriarchal throne, shaped a complex network of relations between the Church and the State, to the extent that on one hand, there was an attempt by the political power to intervene in Church matters, and on the other hand, the leaders of the Church sought to influence or even determine political developments and situations. All these events, some of greater and some of lesser significance, constitute the framework of the ecclesiastical and political history of the period under examination.

In our research, we follow the chronological course of the Byzantine Empire and present the material that directly relates to our examination, while also commenting on certain events that are not directly related to the relations between Church and State. We also thoroughly examine well-known historical events (such as schisms), but primarily analyze them from the perspective of the emperor and the Patriarch's relations. Naturally, we do not provide a comprehensive account of all the events. However, we believe that the ones we analyze give us a clear picture. [...]

(from the book's preface)