Shortly after his Christmas 858 elevation to patriarch, a local council was held in 859 to confirm his appointment formally (rather than risk the ire of the emperor). Supporters of his predecessor Ignatios, however, appealed to Rome for support. Ignatios had been removed and incarcerated solely on the will of the emperor, without trial. These "Ignatians" declared Photios' appointment as patriarch illegitimate.
Pope Nicholas I sent papal legates to Constantinople to conduct an inquiry. By the time they arrived, however, and with the 859 council's confirmation, Photios was firmly established in his role; trying to depose him and restore Ignatios would be difficult and disruptive in its own way. At a synod in Constantinople in 861 they re-affirmed Photios' appointment. Then the legates returned to Rome.
Upon their return, they discovered that Pope Nicholas had wanted an entirely different outcome. In an 863 synod in Rome Nicholas declared Photios deposed and Ignatios restored. Photios held his own synod in which he declared the pope excommunicated for the Filioque heresy. This synod also discussed who had authority over the recently converted Bulgarians, the Eastern Orthodox Church who did the work, or the Roman Church, which felt it had authority over all Christians?
Then in 867 Emperor Michael III was assassinated by a rival who became Emperor Basil I. Basil wanted an alliance with the West, so he sided with the pope, deposed Photios, and reinstated Ignatios. The Fourth Council of Constantinople in 869-870 condemned Photios, officially ending what was considered the "Photian Schism." This council did more than that, however, and deserves its own entry, which it will get next time.