According to tradition, St. Matthew and St. Bartholomew were the first to evangelize Ethiopia in the first century CE, and the first Ethiopian convert was the eunuch in Jerusalem mentioned in The Acts of the Apostles (8:27–40). St. Frumentius later consecrated the first Ethiopian bishop, and Aedesius, two men (likely brothers) from Tyre, further Christianized Ethiopia in the 4th century CE.
They gained the king’s confidence and were granted permission to evangelize in Aksum (a powerful kingdom in northern Ethiopia). Frumentius baptized the succeeding king, Ezana, and Christianity became the state religion. Nine Syrian monks are said to have introduced monasticism to Ethiopia at the end of the fifth century, promoting the translation of the Bible into the Ge’ez language.
In opposing the Christological decision issued by the Council of Chalcedon in 451 CE that the human and divine natures of Jesus Christ were equally present in one person without commingling, the Ethiopian church adopted the Coptic (Egyptian) church (now called the Coptic Orthodox Church of Alexandria).
Miaphysitism holds that divinity and humanity are joined in one nature in the one individual of Jesus Christ, where Christ is consubstantial with God the Father, without division, misunderstanding, modification, or mixing. About 500 bishops from the patriarchates of Alexandria, Antioch, and Jerusalem declined to embrace the dyophysitism (two natures) doctrine decreed by the Council of Chalcedon in 451, leading the Roman Empire’s main church to split for the second time.
The Oriental Orthodox Churches adopt Cyril of Alexandria’s miaphysitic Christological view, which advocates one nature of the Word of God incarnate and a hypostatic union, as advocated by Cyril of Alexandria, the leading protagonist in the Christological debates of the 4th and 5th centuries. This position differed in that the incarnate Christ has one nature, but that nature is made up of the two natures, divine, and human, and retains all of their characteristics after the union.