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.
Yellowstone Expedition of 1873 of the hill along the Yellowstone River. George Custer, with Companies A and B of the 7th Cavalry under the command of Captain Myles Moylan scouted to the west ahead of Stanley's column. Custer's group consisted of 86 enlisted men, 4 officers, and Indian scouts. Custer's brother, First Lieutenant Thomas Custer, and his brother-in-law, First Lieutenant James Calhoun, accompanied him. Shots were exchanged with Sioux Warriors near the Yellowstone River early in the battle, and George Custer's men formed a skirmish line. A volley from the line distracted the pursuing Indians enough to halt the warriors' charge. Custer had Captain