The route had been used by several thousand emigrants in 1864 and 1865 before consistent Lakota opposition began to make it genuinely dangerous.

By 1866, it was effectively under contest — emigrants were attempting to use it, Lakota warriors were attacking emigrant parties with enough success to make the route costly, and the U.S. government had decided that the solution was military presence in the form of permanent fortifications.

Colonel Henry Carrington arrived in the Powder River Country in the summer of 1866 with a force of about seven hundred men and orders to build three forts at strategic points along the trail.

He was not a combat veteran — his service in the Civil War had been primarily in administrative and organizational roles — and he was leading a command that included many raw recruits who had never seen combat of any kind.