1866 On December 21, 1866, a battle occurred between Sioux, Cheyenne and Arapahoe warriors and a force commanded by Bvt. Lt. Col. William J. Fetterman. Fetterman and all the men under his command were killed. The battle is known as both the Fetterman Massacre and The Battle of The Hundred Slain. When Fort Fetterman was established in 1867, it was named for the Lieutenant Colonel.