The Fourth Council of Constantinople was a significant assembly that convened under the auspices of Byzantine Emperor Basil I in 870. It was primarily aimed at resolving the ongoing Photian schism, which had divided the Eastern Orthodox Church due to the contentious appointment of Photius as the patriarch of Constantinople. This assembly gathered numerous bishops and church leaders, primarily from the Byzantine Empire, to discuss theological disputes that had led to division. One of the pivotal aspects addressed was the relationship between the Eastern and Western churches, which had been fraught with tension regarding authority and doctrine.

Throughout its sessions, the council sought to address controversies surrounding the legitimacy of Photius's patriarchate and solidify episcopal authority in the Byzantine realm. It extensively examined various theological positions, ultimately reaffirming the Nicene Creed while also providing new guidelines for ecclesiastical conduct and governance. The closure of the council marked a notable triumph for Photius, solidifying his position and affording a level of doctrinal consistency that the church had previously been struggling to maintain. This decision had profound implications for the unity of the church and the delineation of church governance moving forward.

Moreover, the decisions taken during the Fourth Council played a crucial role in shaping the Byzantine church's approach to Western influences and the Roman Papacy. This period solidified the east-west schism that would culminate in more formal divisions in subsequent centuries. In addition, the council's canons focused on the importance of the role of local synods in making ecclesiastical decisions rather than centralizing authority in specific high offices. As such, it laid the groundwork for future church governance and theological disputes that would resonate throughout medieval Christendom.