schism · 863–867 · Constantinople
When Nicholas I refused to recognize Photius and claimed jurisdiction over Bulgaria, Constantinople answered in kind: synods at Rome (863) and Constantinople (867) deposed and anathematized across the sea. Basil I's coup and the councils of 869 and 879 closed the breach — but Photius' encyclical had named the filioque, and the argument never went away.
Rome's refusal of Photius and the contest over the new Bulgarian church.
Mutual depositions and anathemas (863–867); communion patched, then mended at the council of 879 — but the filioque had now been named between East and West.