The village’s inhabitants — primarily women, children, and elderly — had been assured by American officials that they were under military protection.

Black Kettle, the principal Cheyenne leader, had even flown an American flag over his lodge as a sign of the group’s peaceful status.

The attack killed approximately 150 to 200 people, the vast majority of them women and children.

The massacre was brutal even by the standards of frontier violence.

Congressional investigations confirmed what had happened and condemned Chivington.

But the investigations produced no criminal charges, no legal accountability, and no lasting protection for the communities that were at risk of similar attacks.

For Red Cloud and the other Lakota leaders who knew what had happened at Sand Creek — and they did know, because the Northern Cheyenne who had survived and escaped brought the news across the plains — the lesson was explicit.