Bad behaviour

Bad behaviour on both sides added to the confrontation.

The US government regularly broke its treaty promises - as the Sioux Chief Gall said:

quote
If we make peace, you will not keep it

Meanwhile, some Native Americans wanted war. Early travellers on the Plains were robbed and murdered. And when some Native Americans made peace with the US government, others would stay out on the warpath - white Americans could not understand that the chiefs had no power to make their warriors obey.

American Plains BattlesMap illustrating the key battles of the Great Plains between 1862 and 1890

In 1866, a group of Native Americans wiped out a unit of US cavalry (the Fetterman Massacre), and events like this, and the defeat at Little Bighorn (1876), made the white Americans determined to win the war.