The Opata fiercely resisted the expedition of Spanish explorer Francisco Ibarra in 1565 and for a period of 60 years thereafter, the Spanish made no further attempts to conquer the Opatería. However, during that period, the statelets declined and were replaced, in part, by a much-reduced population, and a “ranchería” culture of small settlements and dispersed dwellings. The likely cause of the decline of the statelets and population were epidemics of introduced European diseases, which killed thousands of the Opata and neighboring peoples. Jesuit missionaries established a mission in Opatería in 1628 and initially encountered little opposition to their efforts to evangelize, and later, to re-organize Opata society along Spanish lines. The Opata slowly became Spanish allies of convenience. Opata soldiers joined the Spanish in campaigns against their common enemy the Apache. By 1800, the Opata were mostly followers of Christianity, commonly spoke Spanish, and were largely under the rule of the Spanish government. Many Opatans became cowboys on Spanish ranches, or migrated to mining towns to work in the mines.