Coonan Cross Oath

The Coonan Cross Oath (Koonan Kurishu Satyam), taken on 3 January 1653, was a public avowal by members of the Saint Thomas Christian community of Kerala, India that they would not submit to Portuguese dominance in ecclesiastical and secular life. The swearing of the oath at Mattancherry was a major event in the history of the Saint Thomas Christian community and marked a major turning point in its relations with the Portuguese colonial forces. The oath resulted in the breaking up of 54 years of Portuguese Padroado (Patronage) Jurisdiction over the Malankara Syrian Church, started with the synod of Diamper inde 1599 A.D. convoked by the Portuguese Archbishop Dom Alexio De Menezes.

The Saint Thomas Christians remain in communion with the Church of the East. It is believed that Malabar Church was in communion with the Church of the East from CE 300 to CE 1599. With the establishment of Portuguese power in parts of India, clergy of that empire, in particular members of the Society of Jesus (Jesuits), attempted to Latinise the Indian Christians.

The Portuguese started a Latin Rite diocese in Goa (1534) and another at Cochin (1558), and sought to bring the St.Thomas Christians under the jurisdiction of the Portuguese padroado and into the Latin Rite of the Catholic Church. A series of synods, including the 1585 Synod of Goa, were held, which introduced Latinized elements to the local liturgy. In 1599 Aleixo de Menezes, Archbishop of Goa, led the Synod of Diamper, which finally brought the Saint Thomas Christians fully under the authority of the Latin Archdiocese of Goa.

...
Wikipedia