From Lakota America: A New History of Indigenous Power, by Pekka Hämäläinen (The Lamar Series in Western History; Yale U. Press, 2019), Kindle pp. 332-335:
The railroad did eventually come, ushering in U.S. troops and U.S. authority, but well before it came Lakotas. Raids into the Crow country and American settlements in the Gallatin Valley became a routine with Sitting Bull serving as a gravitational force…. Suddenly all American settlements “within the reach of the Sioux hunting-grounds” were in danger. The Carroll Trail, a crucial transportation line connecting Helena to the Missouri River, was in risk of being cut off. At times it seemed it was Crows who protected Americans against Lakotas rather than vice versa. Both settlers and soldiers saw the Crows as an extra “regiment of cavalry.”
But the Crows were Lakotas’ primary target, for they stood between them and the bison. Crows were at times forced to flee their reservation in the face of massive Lakota war parties seeking game, horses, mules, and cattle, and their powerless agent seemed to accept “the annual Sioux invasion” as a fact of life. Such was the Lakota pressure that Crow chiefs were rumored to be considering “an offensive and defensive alliance with the Sioux as against the whites.” There could be no such alliance, of course—the game was too scarce and the hatreds ran too deep—and Crows remained close allies of the United States. Before long, Lakotas occupied “the larger and most fertile portion of their reservation.”
Like Crows, Shoshones looked to Americans for protection against Lakotas and their allies. But unlike Crows, they managed to put distance between Lakotas and themselves. Decades of fighting over hunting rights had left them debilitated, and they had accepted a reservation in the lee of the Wind River Range, far to the southwest of the Lakota sphere of operations. Yet, even there, fear of Lakota attacks forced them to periodically flee. Eventually, they ceded a mineral-rich section of their reservation to secure the government’s goodwill and protection. This, in the minds of U.S. agents, was a sign of supreme wisdom: they “are among the most intelligent and best disposed of any Indians on the plains,” gushed the governor of the Wyoming Territory. “Wash-a-kie, their chief, is in all respects a superior Indian.” Their agents reported a growing consumption of government rations—beef, bacon, flour, and sugar—which indicated that Shoshones were giving up the hunt.
So were Utes. They had secured a large eighty-seven-thousand-square-mile reservation in the new Colorado Territory in 1861, but in 1868 they were compelled to accept a much-reduced domain. Five years later the government imposed another reduction, which broke Ute power. Lakota-Arapaho-Cheyenne war parties pushed deep into Ute territory, and growing numbers of Ute hunters began to frequent Denver, expecting to be fed, much to the exasperation of the city’s inhabitants and the territory’s Indian agents: “Even were they ever so well able to pay for hotel accommodations, they are not a desirable class of customers to the proprietors of any of our public-houses.” In the summer of 1873 Ute hunters wished to parade enemy scalps on the streets of Denver: they had killed three Lakota warriors while hunting along the Republican. The Indian agent banned the parade, and Utes celebrated their surprising victory outside the city for a week. It was clear that there would not be many more. Agents reported “improved industrial habits,” larger crops, and a growing willingness to live in houses.
Establishing control over shrinking bison herds was the paramount motive of Lakota warfare in the early 1870s, and it spawned a sprawling raiding hinterland that extended from the Canadian plains into the Rockies and deep into the American Southwest. Closer to home, Lakotas waged a sporadic raiding war against the Arikaras, Hidatsas, and Mandans who now shared a reservation along the Missouri and Little Missouri Rivers. Lakota war parties raided the reservation for horses and corn with growing confidence, sometimes coming with women and often informing their agents of their intentions and successes. Arikaras retaliated by raiding Lakotas at their Grand River and Cheyenne River Agencies, but their agent wanted to move them to Indian Territory, farther away from Lakotas. He was promptly rebuffed: “they fear that it is too warm for them. . . . Besides they love their own country; their dead are buried here; the Government probably would not redeem its promises better there than here.” For Arikaras the U.S. Indian policy was a demoralizing exercise in hypocrisy. “‘The hostile Sioux have all they want from the Government without removal from their country,’” their chiefs protested. “‘Why cannot the Rees [= Arikaras], who have been so friendly and faithful these many years?’” The Arikaras stayed put, their numbers slowly declining in the shadow of an overpowering Lakota-U.S. alliance.
As their rivals yielded ground, Lakotas emerged, in many ways, more powerful than ever. Never before had they ranged over more territory or reached so far. Their core area—their homeland—exceeded the Great Sioux Reservation by tens of thousands of square miles, and their hunting and raiding domain stretched from Lake Winnipeg in the north to the Republican Valley in the south and from the Missouri Valley in the east to the Continental Divide in the west. They had thousands of Indigenous allies on their orbit and diplomatic and commercial ties to Canada and Washington, D.C. They had several handsomely stocked government agencies at their disposal, and they went to war with cutting-edge military technology. Formidable, flexible, and ubiquitous, they commanded the attention of the U.S. government like no other Indigenous nation.