Their leader was a Syrian who is known to history as Knae Thomman, Thomas Cananeus, Thomas of Cana, or Thomas the Merchant. They were four hundred refugees belonging to seven tribes of West Asia, who were fleeing religious persecution by the Persian Shapor II.
The consensus among most historians who do not have a theological axe to grind, is that the first Christians to arrive in India, landing at Cranganore, Kerala, came in 345 CE.