The Big Horn Expedition, or Bighorn Expedition, was a military operation of the United States Army against the Sioux, and Cheyenne Indians in Wyoming Territory and Montana Territory. Although soldiers destroyed one Cheyenne and Oglala Sioux village, the expedition solidified Lakota Sioux and northern Cheyenne resistance against the United States attempt to force them to sell the Black Hills and live on a reservation, beginning the Great Sioux War of 1876.