Some debate exists over whether Hernando de Soto was the first Spanish conquistador to encounter Native Americans in this area, but he is known by his chroniclers to have passed through the region in 1540 with his expedition across the interior of the Southeast. In 1560, Tristán de Luna sent a detachment of 140 soldiers and two Dominican friars north along de Soto's route. They established relations with the Coosa chiefdom, as they recorded assisting the Coosa in a raid against the rebellious province of Napochín, in what is now known as Tennessee. Exposed to new Eurasian infectious diseases, the Coosa and other indigenous peoples suffered high mortality rates, as they lacked immunity. Within 20 years the Coosa chiefdom was abandoned.