The massacre of about 600 to 700 Christians in Mannar in 1544 by Cankili I enraged Catholic priests, who complained to the Portuguese authorities in Goa. The Portuguese did not carry out any reprisals, however, as they were facing hostilities in India. The complaint eventually reached the KingJoão III, who ordered his forces at Goa to punish the King of Jaffna for his actions. There was a delay in carrying out the order. When Dom Constantino left Portugal in 1558, Queen Catherine instructed him to execute the king's order, which had been delayed for various reasons. She ordered that the king of Jaffna should be punished especially for the Mannar massacre and the continuing persecution of Christians.
Battle
Dom Constantino sailed in September 1560 from Goa to Jaffna with 20 galleys, 10 galiots, and 70 ships. The forces consisted of 1,200 soldiers; that small number of troops was unfit to carry out the planned invasion. The forces reached the shore of Colombuthurai, where they were met by the Jaffna forces of 2,000 soldiers led by a prince. The heavy artillery barrage from the Portuguese ships inflicted significant casualties on the Jaffna forces, and as a result, the Portuguese forces were able to reach land and advance on the capital. The capital was located on an open plain and fortified by stones and sands, with some strong bastions provided with artillery and much infantry. The capital fell to the Portuguese and the king withdrew his forces to a small fort in Kopay. Before the next day's dawn, the palace was set afire and the king escaped to the Vanni region. A group of Portuguese soldiers followed in an attempt to capture him, but were unsuccessful.
Pact
Acknowledging that he was not in a position to repel the enemy forces, the king sent Dom Constantino to sue for peace. The viceroy seized the opportunity, as he had limited troops and was short of food and ammunition. The provisions of the pact signed between the warring parties were as follows:
The king and his son were allowed to continue to rule the kingdom
Control of Mannar Island and the western shore would be ceded to the Portuguese
Jaffna forces were not permitted firearms and other explosive weapons
Jaffna was not allowed to employ foreign forces
Portuguese forces were permitted to remain in Jaffna
The hidden treasury of the father of the Kotte king was to be handed over to the Portuguese
Every year a certain number of elephants would be provided to the Portuguese as a tribute
