Moving on, the wars started like most wars, greed and pride. The settlers were greedy when gold was discovered, and refused to acknowledge the local population's claim on the land. The Indian tribes in the area retaliated (rightfully so), and started killing settlers. Then the back and forth began, and did not end for quite some time. Gold is what started the wars, the United States Army's Cavalry ended it.
The gold aspect was the result of the Black Hills gold rush. Like most gold rushes in the 1800s, prospectors came rushing in with no regard to any land claims of anyone else. The united states developed trade routes through hunting lands of the local tribes, which eventually led to bloodshed (Watkins, 2018). Red cloud was very successful in his campaigns, and received almost all of his demands in the Treaty of Fort Laramie in 1868. They ended with the United States eventually dedicating the bulk of their military resources to beating the Amerindians into submission. Part of this was the concept of "total war" that General Sherman used is the Civil War (Davis, 2018). Kill enough civilians, and eventually a people will no longer have the will to fight.
Obviously, conquest affects a people in a negative manner. The local tribes were corralled into reservations. All who refused to submit were either killed or imprisoned. The last major battle was the Red River war. This was pretty much the end of the Plains Indians way of life (Davis, 2018). Of course, there was the infamous Geronimo, he was loved by some, and hated by others. However, he definitely left an impression for eternity of the fighting spirit of the Plains Indians.
None of this would have happened if the Euro-Americans had never settled further and further west. However, where there's gold, there's interested parties. The biggest barrier used was harvesting the bison to near extinction in the west. The Plains Indians Depended on these bison as a main food source. Without them, they had to rely on the United States Government to provide food and supplies. This made forcing them into reservations all the easier (Watkins, 2018).