The Photian Schism was a four-year (863–867) schism between the episcopal sees of Rome and Constantinople. The issue centred on the right of the Byzantine Emperor to depose and appoint a patriarch without approval from the papacy. In 857, Ignatius was deposed or compelled to resign as Patriarch of Constantinople under the Byzantine Emperor Michael III for political reasons. He was replaced the following year by Photius. The pope, Nicholas I, despite previous disagreements with Ignatius, objected to what he considered the improper deposition of Ignatius and the elevation of Photius, a layman, in his place. After his legates exceeded their instructions in 861 by certifying Photius's elevation, Nicholas reversed their decision in 863 by condemning Photius. The situation remained the same until 867. The West had been sending missionaries to Bulgaria. In 867, Photius called a council and excommunicated Nicholas and the entire western Church. That same year, high ranking courtier Basil I usurped the imperial throne from Michael III and reinstated Ignatius as patriarch.