or Chivington Massacre
(Nov. 29, 1864) Surprise attack by U.S. troops on a Cheyenne camp.
A force of 1,200 men, mostly Colorado volunteers under Col. John M. Chivington, attacked several hundred Cheyenne camped on Sand Creek near Fort Lyon in southeastern Colorado Territory. The Indians had been conducting peace negotiations with the fort's commander; when the attack began, they raised a white flag, but the troops continued to attack, massacring more than 200 of them. The slayings led to the Plains Indian wars.