According to the tradition, St Thomas came by sea and landed at Kodungalloor (Cranganore) the capital of the then Chera Empire in 52 AD.
According to Malabar tradition St Thomas founded seven churches, they are in Cranganore, Quilon, Chayal, Kokkamangalam, Niranam, Paravur and Palayur.
It is worth mentioning that the Apostle gave his followers a way of worship suited to their clime, culture and customs.
Thus the Indian Church became a member of the Babylonian (also known as Assyrian & Syro-Chaldean) Patriarchate for practical purpose, not for doctrinal reasons.
Because of the close association of the St Thomas Christians with the East Syriac Church, the Indian Church of St Thomas is classified in history under the Chaldean matrix of rites, as we read in CCEO C.28:2 As Pope Pius XII said "during the centuries that India was cut off from the west and despite many trying vicissitudes, the Christian communities formed by the Apostle conserved intact the legacy he left them, and as soon as the sea passage at the close of the 15th century offered a link with their fellow Christians of the west, the union with them was spontaneous" (AAS, XLV (1953) pp.
Bulls of Pope Julius III dated 10 March 1553 and 4 May 1553 in Giamil, "Genuinae Relationes....." Rome 1902, PP.