Apparently, much of the lands that were given over to the native american tribes were not suitable for sustained agriculture, and the game was quickly exhausted. That being the case, several tribes began raiding neighboring ranch lands for cattle employing guerilla tactics. Evidently, because of this and other cultural prejudices, hostilities were soon fermented and escalated. Also, some tribes were angered by perceived encroachments upon their territories. Militias were soon formed by 'white' settlers for the express purpose of the eradication the natives, continuing the governments previous policy of what should be considered as borderline genocide. There is a record of some chieftains visiting Lincoln at Washington in 1863, where he may have tried to appease them, but more likely wanted to show them the dominance and potency of the federal government. I haven't been able to read what Lincoln may have told them.