The Malankara Orthodox Syrian Church, also known as the Indian Orthodox Church, is an autocephalous Oriental Orthodox church centred in the Indian state of Kerala. The Malankara Orthodox Syrian Church was founded by St. Thomas, one of the twelve apostles of Jesus Christ, who came to India in A.D. 52. The church is headed by the autonomous Catholicos of the East; Baselios Mar Thoma Paulose II became Catholicos of the East and the Malankara Metropolitan on 1 November 2010.
Saint Thomas Christians were administratively under the single native dynastic leadership of Arkadyaqon (East Syrian term for an ecclesiastical head with extensive administrative powers, deriving from Greek αρχιδιάκονος = archdeacon) and liturgically it was a part of the Church of the East centered in Persia.[4][5] It was not necessary for the Malankara Church to oppose or adhere to Nestorianism as they were outside Roman and Persian empires and the Royal Cheran or Pandiyan kings never interfered in matters of their faith. The indigenous Eastern Church of Malabar/Kerala followed the faith and traditions handed over by the Apostle St. Thomas, and most of the early churches were named after St. Mary. During the period of Colonialism, (i.e., from the 16th century), the Portuguese Jesuits began deliberate attempts to annex the community into the Latin Rite of the Catholic Church, and in 1599 A.D., they succeeded in their attempt through the infamous Synod of Diamper. Resentment against these forceful measures led the majority of the community under their Arkadyaqon Thomas to swear an oath never to submit to the Portuguese, known as the Coonan Cross Oath in 1653. It prompted the Portuguese to call the native Malankara Nazranis consolidated under the Arkadyaqon as ‘Puthenkootukar’ (new traditionlists) and the Roman supporters as ‘Pazhyakootukar’ (old traditionalists) to hide the new Latin hierarchy introduced in Malabar. In fact, Latin rites introduced in Malankara by Aleixo de Menezes, the Catholic Archbishop of Goa, was much more strange and embarrassing than West Syrian rites for Malabar Christians who were genetically accustomed with Syrianism of Asiatic Christianity.
The Dutch East India Company defeated Portuguese for the supremacy of spice trade in Malabar in the year CE 1663. Malankara Nazranis used this opportunity to escape from Latin persecution with the help of Dutch East India Company. The Dutch brought Bishop Gregorios Abdul Jaleel of Jerusalem of Syrian Orthodox Church in their trading vessel in CE 1665. Thomas Arkadyaqon who was consecrated as Mar Thoma I forged a relationship with the West Syriac Orthodox Church and gradually adopted West Syrian liturgy and practices. The church is theologically and traditionally a part of the Oriental Orthodox communion of churches. The Indian Orthodox Church accepts the Miaphysite Christology of St Cyril of Alexandria and uses the Malankara Rite, a local variant of the West Syrian Rite. The members of the Church are known as Malankara Nazaranis or Marthoma Suriyanis.