The prospectors grazed their livestock on Cheyenne hunting grounds, scared away the game, and simply occupied land that the 1851 treaty had recognized as Cheyenne country.

The territorial government of Colorado that emerged from this situation was dominated by people who wanted the Cheyenne and Arapaho removed.

John Evans, the territorial governor appointed by President Lincoln in 1862, and John Chivington, the commanding military officer, were both committed to the view that the Cheyenne and Arapaho needed to be driven from Colorado — and both were willing to use violence to accomplish this.

The situation was made more complicated by the Civil War, which drew most of the regular Army away from the frontier and left the defense of the Colorado Territory in the hands of volunteer forces.