Saint Dalmatius was a saint

Saint

A saint is a holy person. In various religions, saints are people who are believed to have exceptional holiness.In Christian usage, "saint" refers to any believer who is "in Christ", and in whom Christ dwells, whether in heaven or in earth...

 venerated in Constantinople

Constantinople

Constantinople was the capital of the Roman, Eastern Roman, Byzantine, Latin, and Ottoman Empires. Throughout most of the Middle Ages, Constantinople was Europe's largest and wealthiest city.-Names:...

. His feast day was August 3. An archimandrite

Archimandrite

The title Archimandrite , primarily used in the Eastern Orthodox and the Eastern Catholic churches, originally referred to a superior abbot whom a bishop appointed to supervise...

, he was an opponent of the Nestorians

Nestorianism

Nestorianism is a Christological doctrine advanced by Nestorius, Patriarch of Constantinople from 428–431. The doctrine, which was informed by Nestorius's studies under Theodore of Mopsuestia at the School of Antioch, emphasizes the disunion between the human and divine natures of Jesus...

.

Following Cyril of Alexandria

Cyril of Alexandria

Cyril of Alexandria was the Patriarch of Alexandria from 412 to 444. He came to power when the city was at its height of influence and power within the Roman Empire. Cyril wrote extensively and was a leading protagonist in the Christological controversies of the later 4th and 5th centuries...

's instructions, Dalmatius lead a mob to attack the palace of Theodosius II

Theodosius II

Theodosius II , commonly surnamed Theodosius the Younger, or Theodosius the Calligrapher, was Byzantine Emperor from 408 to 450. He is mostly known for promulgating the Theodosian law code, and for the construction of the Theodosian Walls of Constantinople...

, and shout abuse against him, because he had sided with the Nestorians and annulled the First Council of Ephesus. Although the Emperor subsequently gave in, the events created a major schism

Schism (religion)

A schism , from Greek σχίσμα, skhísma , is a division between people, usually belonging to an organization or movement religious denomination. The word is most frequently applied to a break of communion between two sections of Christianity that were previously a single body, or to a division within...

, forming the Assyrian Church of the East

Assyrian Church of the East

The Assyrian Church of the East, officially the Holy Apostolic Catholic Assyrian Church of the East ʻIttā Qaddishtā w-Shlikhāitā Qattoliqi d-Madnĕkhā d-Āturāyē), is a Syriac Church historically centered in Mesopotamia. It is one of the churches that claim continuity with the historical...