The following is from the book, The New Encyclopedia of the American West, by Howard R. Lamar.
December 21, 1866: The Fetterman Massacre was fought near Fort Phil Kearny, Wyoming, between Sioux, Cheyenne, and Arapaho warriors and 80 men under the command of Brevet Lieutenant Colonel William J. Fetterman. Fetterman's detachment was annihilated.
Resentful of the intrusion of white soldiers into unceded Indian lands, the Plains tribes constantly harassed Fort Phil Kearny's undermanned and poorly equipped garrison and raided its wood and supply parties. During such an attack on the wood train, post commandant Colonel Henry B. Carrington ordered Fetterman's command to its relief. The Indians had carefully planned an ambush, and although the wood train escaped to the fort, Fetterman's troops perished to a man. In the furor that followed the incident, Carrington was relieved of is command, and his military career was virtually ended.
Historians have tended to accept Carrington's assertion that Fetterman had disobeyed orders and therefore was to blame for the catastrophe; that viewpoint is well presented in Dee Brown, Fort Phil Kearny: An American Saga (1962). J.W. Vaughn, however, has argued in his Indian Fights: New Facts on Seven Encounters (1966) that Fetterman instead was probably following an order by Carrington to make an offensive movement against the small group of Sioux that had ridden out to decoy the soldiers into a trap and that Carrington's story was an attempt to shift the blame from himself. Because there is much conflicting testimony, which is difficult to resolve, the full truth of the episode will probably never be known. The Indians' version of the battle is related in George Bird Grinnell, The fighting Cheyennes (1915). For a more recent study, see Robert M. Utley, Frontier Regulars: The United States Army and the Indian, 1866-1891 (1973). - J.T.K.