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.
Battle of the Rosebud on the reservation by January 31, 1876 to negotiate the sale. A few bands did not comply and when the deadline of January 31 passed the US undertook to force Sitting Bull, Crazy Horse, and their followers onto the reservation. The first military expedition against the recalcitrant Indians in March 1876 was a failure, ending in the Battle of Powder River. In June 1876, the US military renewed the fight with a three-pronged invasion of the Bighorn and Powder river country. Colonel John Gibbon led a force from the west; General Alfred Terry (with Lieutenant Colonel George Armstrong Custer) came