The cause of the conflicts was like many of the Indian Wars. In 1684, the Spanish colonists in the present day Mexican state of Sonora discovered silver in the Rio Yaqui Valley. Following this, the Spanish gradually began settling on Yaqui land, and by 1740, the natives were ready to resist. Some minor conflicts from before dated back to 1533 but in 1740 the Yaqui united with the neighboring Mayo, Opata, and Pima tribes and successfully drove the colonists out by 1742.. How many years after the discovery of silver did the natives show resistance towards the colonists?