 Portuguese attempted various methods to subjugate, such as by sending religious missions in the 16th-century to convert the people into cooperative Catholics, but the members of such missions were suspected of bad intentions and killed.Through the 18th-century, Portugal partially succeeded in controlling the Zambesi river valley by granting Portuguese settlers imperial rights over the land with Portuguese military protection, with the settler-landowner called "Prazeiro" had the right to tax and exploit local people as labor, in exchange for tribute payments.Rebellions were common, but sporadic and lacked cohesion between various ethnic groups including the Sena, Tonga and Tawara peoples and sometimes within the same ethnic group.