Although I have some Cherokee blood in me, one of my ancestors also served as one of Custer's scouts during the infamous attack on Black Kettle's band of women, children, and elderly camped on the Washita River.
As mentioned above, read "Son of the Morning Star," which was the nickname many Indians had for Custer during the nine or so years between the time he massacred literally hundreds of women and children under the light of Venus (the Morning Star) and Little Big Horn.
Colonel John M. Chivington, also responsible for the Black Kettle Massacre if I remember my history, told his men to kill all Indians, saying "...kill and scalp all, little and big... nits make lice."
I think both sides practiced "kill 'em all" for the most part.
Then again, the response of the Indians was to slaughter entire wagon trains of pioneers with such savagery, using live prisoners for target practice, or butchering the men while alive, flaying them etc. and gang raping the women until they died from loss of blood.
The operative philosophy of the US Govt at the time was "the only good Indian is a dead Indian." To some extent, they brought it on themselves early in our history. There were friedly tribes and warring tribes. The warring tribes sometimes sacked entire small communities. Their philosophy requiring that they kill 10 enemy for every brave lost in battle.
Well, the Judeo-Christian Western society developed to generally sparing non-combatants, women and children. The warring tribes sometimes sacked entire small communities -- their philosophy requiring that they kill 10 enemy for every brave lost in battle. It didn't take too many instances of seeing multiple massacres of women and children to convince the general public that Indians were "savages" (so called because they weren't baptized Christians) and their fate was sealed with a decision to mass exterminate all members of the warring tribes.
I remind my liberal friends of these good old days when they tell me modern Americans are so uncivilized. I agree, but only with respect to the 40 million aborted (murdered) babies since 1970.