The federal government traditionally treated the tribes like sovereign nations, establishing treaties along the way. However, pressure from white settlers to expand always led to broken promises. The government established a "concentration" policy in 1851 in which each tribe was given a reservation, which was mostly undesirable land. This was replaced with a different policy in 1867 to move the Plains Indians into two large reservations. They were poorly administered by the Bureau of Indian Affairs.
Get outta 'ere.
I thought we had a treaty.
As the tribes were being relocated, their way of life was being destroyed. Whites began slaughtering buffalo herds for their meat, for their hides, and to get rid of the obstruction to railroad traffic. Settlement also threatened the buffalo. The decimation of the buffalo population destroyed the native source of food and supplies. Some felt the need to fight to preserve their way of life
You take my land and now this?
Between the 1850s and 1880s there was nonstop fighting between whites and Indians. Indians attacked wagon trains, stagecoaches, and ranches, often in retaliation for earlier attacks. As the US Army became involved, attacks were directed more against the soldiers. Small-scale fighting sometimes escalated to war levels. For example, the eastern Sioux in Minnesota, led by Little Crow, killed over 700 whites before being subdued. Additionally, white vigilantes were also engaging in "Indian Hunting," perpetuated by bounties and ideas of racial superiority.