Next to Photius and Michael Cerularius, Nicholas I is probably the most prominent of the patriarchs of Constantinople. He was the central figure in the “tetragamy” affair, the conflict over Leo VI’s fourth marriage, which divided the Church for nearly a century and resulted in Nicholas’s temporary deposition. He was also a major influence in both the domestic and foreign politics of the Eastern Empire throughout the first quarter of the tenth century. His correspondence with the Papal court and with Bulgarian, Caucasian, and Arab provinces, as well as with his own clergy, is a historical source of the first importance.

This volume is supplemented by Nicholas I, Patriarch of Constantinople: Miscellaneous Writings (CFHB XX, DOT VI).