As you may know, there are many different variations on what happened in Montana at the little Big Horn a few days before the nation's hundredth anniversary.
Anyway, here's some of the information that's been released, though there were many more tribes than are usually listed that (understandably) participated. My understanding is that Sitting Bull was in a nearby encampment but did not engage the enemy, though he had a pre incidental vision of Custer's impending defeat.
He (Custer) was warned, many times, by his scouts that there were about 1,500 combatant Native Americans (not counting the women and children) and that they were armed with Winchester repeating rifles, as compared to most of Custer's men being armed with .50 caliber Sharps single shot rifles and six guns with no spare ammunition. The Sharps rifles were overheating and jamming.
The entire tribal council of Hunkpapa, Teton, Lakota and Dakota tribes were there, representing the Sioux Nation. There were also Cheyenne, Blackfoot, Nez Perz and Sans Arc tribal warriors. They were particularly bellicose, because Custer was intruding on a religious pilgrimage.
Custer had the option of including two different wheeled Gatling guns with his troopers, but rejected the opportunity 'because they'll slow me down'.
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