Mar Thoma Darmo, a native of Mesopotamia, was Metropolitan of the Assyrian Church of the East from 1952 to 1968, based at Trichur, Kerala, India. In schism against the Catholicos Patriarch Mar Eshai Shimun XXIII because of reform issues introduced by the Assyrian Church of the East, he voiced his opposition and as a result the rival Ancient Church of the East was established in 1964. Subsequently Mar Thoma Darmo was elected as head of the new church as its first Catholicos-Patriarch in October 1968.