Thomas Mower McDougall subsequently he was appointed Captain, 15 Dec 1875. In 1876 Captain McDougall commanded Company B and accompanied the 7th Cavalry Regiment, under command of Lt. Col. George A. Custer in its fateful departure from Fort Abraham Lincoln to participate in what became known as the Great Sioux War of 1876, which culminated in the Battle of the Little Bighorn, also known as Custer's Last Stand which occurred on June 25–26, 1876. On May 17, 1876, the 7th Cavalry left their base at Fort Abraham Lincoln near present day Mandan, North Dakota to join in a campaign against the Sioux Indians.
9th Cavalry Regiment (United States) scouting for hostile natives, escorting the mail, surveying uncharted land, and constructing roads. That service also included the Battle of Tularosa with Chiricahua Apache warriors led by Victorio in May 1880. The 9th Cavalry was transferred to Fort Riley, Kansas, in 1881, and to Fort Robinson, Nebraska, in 1885. On 5 November 1887, Company H, of the 9th Cavalry fought at the Battle of Crow Agency during the Crow War, at Crow Agency, Montana. The regiment was also patrolled during the Ghost Dance War with the Sioux around the time of the Wounded Knee Massacre and were the last regiment