First it seemed they could be united. Then the Alexandrians reacted, but they reacted so much and so victoriously that Rome took the side of Antioch. But Rome put a condition to the Antiocheans. They had to remove Nestorius because he was now too much suspect. After a synod in Ephesus in 431, in which a compromise was prepared and (also) many further synods – the famous latroceneum Ephesum ,the synod of “gangsters,” as they were called, because they came with sticks to drive each other out, and they transported hundreds of monks to the doors of the church where the synod took place, in order to threaten everybody who would deny the theotokos of Mary, God walking on earth.
After all this, the final and most famous synod, that of Chalcedon, took place in 451, the only other date (together with Nicaea, 325) which I would like you to know. In the Synod of Chalcedon, the alliance of Rome and Antioch proved its strength. They were very much supported by the fact that one of their opposition, the bishop of Alexandria, Eutychus, put forth such a radically Monophysitic attitude that he was condemned. This condemnation of Alexandria was at the same time the victory for Antioch.
How does this decision of Chalcedon look? Decisive for the actual outcome of this synod was that the Roman pope, Leo I, wrote to a synod in Ephesus a letter which was not even read by the victory-drunken Alexandrians, In Chalcedon, however, the letter was accepted as a basic document. There Leo says: “Thus the properties of each nature and substance were preserved entire, and came together to form one person. Humility was assumed by majesty, weakness by strength, mortality by eternity.” “There was one true God in the entire and perfect nature of true man.