William Fetterman was born in Connecticut in about 1833. During the American Civil War he joined the Union Army. He was commissioned as a first lieutenant in the 18th infantry in May, 1861. During the war he received two brevets for gallantry and promoted to the rank of captain. In 1866 he was assigned to Fort Phil Kearny in Wyoming.

June 1866, Red Cloud, chief of the Oglala Sioux, began negotiating with the army based at Fort Laramie about the decision to allow emigrants to settle on the last of the great Sioux hunting grounds. When he was unable to reach agreement with the army negotiators he resorted to sending out war parties that attacked emigrants and army patrols. These hit and run tactics were difficult for the army to deal with and be the time they arrived on the scene of the attack the war parties had disappeared.

On 21st December, 1866, Fetterman and an army column of 80 men, were involved in protecting a team taking wood to Fort Phil Kearny. Although under orders not to "engage or pursue Indians" Fetterman gave the orders to attack a group of Sioux warriors. The warriors ran away and drew the soldiers into a clearing surrounded by a much larger force. All the soldiers were killed in what became known as the Fetterman Massacre. Later that day the stripped and mutilated bodies of the soldiers were found by a patrol led by Captain Ten Eyck.