Determined to challenge the growing American military presence in their territory, Native Americans in northern Wyoming lure Lieutenant Colonel William Fetterman and his soldiers into a deadly ambush on December 21, 1866. With 81 fatalities, the Fetterman Massacre was the army’s worst defeat in the West until the Battle of Little Bighorn in 1876.

Tensions in the region started rising in 1863, when John Bozeman blazed the Bozeman Trail, a new route for emigrants traveling to the Montana gold fields. Bozeman’s trail was of questionable legality since it passed directly through hunting grounds that the government had promised to the Sioux, Cheyenne and Arapahoe in the Fort Laramie Treaty of 1851. Thus when Colorado militiamen massacred more than two hundred peaceful Cheyenne during the Sand Creek Massacre of 1864, the Native Americans began to take revenge by attacking whites all across the Plains, including the emigrants traveling the Bozeman Trail. The U.S. government responded by building a series of protective forts along the trail; the largest and most important of these was Fort Phil Kearney, erected in 1866 in north-central Wyoming.

Native Americans under the leadership of Red Cloud and Crazy Horse began to focus their attacks on Fort Phil Kearney, constantly harassing the soldiers and raiding their wood and supply parties. On December 6, 1866, Crazy Horse discovered to his surprise that he could lead a small detachment of soldiers into a fatal ambush by dismounting from his horse and fleeing as if he were defenseless. Struck by the foolish impulsiveness of the soldiers, Crazy Horse and Red Cloud reasoned that perhaps a much larger force could be lured into a similar deadly trap.

On the bitterly cold morning of December 21, about 2,000 Native warriors concealed themselves along the road just north of Fort Phil Kearney. A small band made a diversionary attack on a party of woodcutters from the fort, and commandant Colonel Henry Carrington quickly ordered Colonel Fetterman to go to their aid with a company of 80 troopers. Crazy Horse and 10 decoy warriors then rode into view of the fort. When Carrington fired an artillery round at them, the decoys ran away as if frightened. The party of woodcutters made it safely back to the fort, but Colonel Fetterman and his men chased after the fleeing Crazy Horse and his decoys, just as planned. The soldiers rode straight into the ambush and were wiped out in a massive attack during which some 40,000 arrows rained down on the hapless troopers. None of them survived.

Further attacks eventually forced the army to reconsider its commitment to protecting the Bozeman Trail, and in 1868 the military abandoned the forts and pulled out. It was one of only a handful of clear Native American victories in the Plains Indian Wars.