From The Earth Is Weeping: The Epic Story of the Indian Wars for the American West, by Peter Cozzens (Knopf, 2016), Kindle Loc. 3858-3875:
After Sitting Bull’s investiture as head of the non-treaty Lakotas, his uncle Four Horns advised him to “be a little against fighting but when anyone shoots be ready to fight him.”
Four Horns’s counsel, however, applied only to whites; Crows continued to be fair game. Sitting Bull and Crazy Horse led the push to dispossess the Crows of their remaining hunting grounds in the early 1870s, but many from the treaty bands fought with them, as did the Northern Cheyennes and, to a lesser degree, their Northern Arapaho allies. The architects of the Fort Laramie Treaty of 1868 had included Crow land within the Unceded Indian Territory, which made Lakota aggression perfectly legal. But it threatened the citizens of southwestern Montana, who had counted on the Crows as a buffer between themselves and Lakotas, and the governor appealed for federal intervention. Generals Sherman and Sheridan made it a matter of unofficial policy to supply the Crows with arms. Each side benefited: settlers felt safer, and the army winked at Crow retaliatory raids against the Lakotas.
The Crows had it hard, but none suffered more for their fidelity to the Great Father than did the Pawnees. Agency Oglala and Brulé warriors raided Pawnee villages in central Nebraska with the implicit support of Red Cloud and Spotted Tail, who saw nothing amiss in young warriors sating their hunger for war honors at the expense of tribal enemies. Certainly it was preferable to unwinnable wars with the whites. In August 1873, at least eight hundred Lakota warriors, perhaps led by Spotted Tail himself, fell upon a Pawnee hunting party in southwestern Nebraska, killing a hundred, of whom nearly half were women and children. Only the timely appearance of a cavalry detachment prevented a greater slaughter.
The massacre broke the spirit of the Pawnees. Nebraskans who recalled the protection that the Pawnees had afforded Union Pacific work crews in their state were outraged and demanded the government give the Pawnees the best available arms in order to meet the Lakotas on an equal footing. Instead, the Indian Bureau banished the Pawnees to Indian Territory. In their single-minded ambition to remake the hostile tribes into white men, the eastern humanitarians did not lift a finger to forestall this unpardonable act of bad faith.