The Powder River Expedition of 1865 also known as the Powder River War or Powder River Invasion, was a large and far-flung military operation of the United States Army against the Sioux, Cheyenne, and Arapaho Indians in Montana Territory and Dakota Territory. Although soldiers destroyed one Arapaho village and established Fort Connor to protect travelers on the Bozeman Trail, the expedition is considered a failure because it failed to defeat the Indians and secure peace in the region.