Nestorius

Nestorius (; "c." 386–"c." 451) was Archbishop of Constantinople from 10 April 428 to 22 June 431. His views were popular in the East.
History.
Nestorius objected to the popular custom calling the Mary (the mother of Jesus), "Theotokos", meaning the mother of god. He believed that Jesus had two parts, one human and one divine. This belief, now called Nestorianism, was different to those held by Cyril of Alexandria, who said that Jesus was both man and god at once. Nestorius said that Cyril was a heretic. At the Council of Ephesus he wanted Cyril charged with heresy. Most of the bishops who agreed with Nestorius came from the eastern churches, and did not arrive at the council meeting before the decision was made. Most of the bishops who were at the meeting agreed with Cyril, and Nestorius was removed from his position as archbishop and sent into exile in Egypt. 
In the east, the churches still supported Nestorius, and did not accept his removal. As a result, they set up their own group of churches, known as the Assyrian Church of the East, in Persia.