The Council of Ephesus meant to heal a rift between Nestorius of Constantinople and Cyril of Alexandria, but instead it set off a chain of ecumenical councils that disagreed with each other, excommunicated rivals, and ultimately led to more factions within the church. Disclaimer: This series is intended for students, to give them a broad overview of a complicated subject that has driven world history for centuries. Our story begins and focuses on the Romane Empire. A centuary after Constantine, the Emperor Theodosius II found himself wrapped up in yet more theological disputes. His chosen patriarch of Constantinople, Archbishop Nestorius, had angered many other church leaders with his teachings that Christ had separate human and divine natures. Cyril of Alexandria wrote to the Pope in Rome for support against Nestorius, and received permission to excommunicate him. Nestorius responded by having the emperor call an ecumenical council, at which he intended to excommunicate Cyril. But Cyril acted first, declaring for the excommunication of Nestorius and forming a majority by pushing the council to begin early before the supporters of Nestorius could gather. When they did, they formed their own council and excommunicated Cyril right back, only to be excommunicated in turn by Cyril's Council of Ephesus. Theodosius II attempted to resolve this by calling a second council, but this time none of the Western delegates had time to arrive and in their absence, monophysite leaders from the East excommunicated Nestorius again and declared monophysitism the official doctrine of the church. Those who didn't get to participate called this the Robbers Council and refused to acknowledge it. Then Theodosius II died, and this fight devolved onto his successor, Marcian. Marcian called together the Council of Chalcedon to rule on the previous councils, where it was finally decided that Christ had two unified natures, human and divine, and everyone who'd supported the Robbers Counci