Prior to becoming Patriarch, Nestorius had been a student of Theodore of Mopsuestia at the School of Antioch.
Nestorius argued that Christ's human and divine natures were distinct and so he was against using the title Theotokos (Greek: "God bearer") for the Virgin Mary.
Cyril of Alexandria considered the doctrine contrary to Orthodox teaching and encouraged measures against it.
The schism ended in 544, when patriarch Aba I ratified the decision of the Council of Chalcedon.
Modern research suggests that also the Church of the East in China did not teach a doctrine of two distinct natures of Christ.