 However, the massive population of the settlers from the east and the diseases they brought with them led to mounting pressure and subsequent decline of the Comanche power and the cessation of their major presence in the southern Great Plains.The Comanche maintained an ambiguous relationship with Europeans and later settlers attempting to colonize their territory.The Comanche were valued as trading partners since 1786 via the Comancheros of New Mexico, but were feared for their raids against settlers in Texas.