Beginning in the latter years of the sixteenth century, and continuing through the seventeenth and eighteenth centuries, Jesuit missionaries made a great pioneering thrust northward along the western coast of Mexico. In this area of Sinaloa-Sonora they met with many fierce and uncultured groups of natives, and frequently they were forced into temporary retreat at the cost of some of their very able men. But their advance was not brought to a permanent halt except by the command of the king which brought to an end all Jesuit activities throughout the Spanish domains.