From Lakota America: A New History of Indigenous Power, by Pekka Hämäläinen (The Lamar Series in Western History; Yale U. Press, 2019), Kindle pp. 46-47:
Seventeenth-century North America was a vast Indigenous ocean speckled with tiny European islands. The Spanish, English, and French newcomers claimed vast chunks of the continent through the doctrines of discovery and terra nullius (no one’s land), but such claims mattered little on the ground where the Indians controlled the balance of power. Through shrewd diplomacy, warfare, and sheer force of numbers, the Indians held the line. In 1700 French settlement remained tethered to the St. Lawrence and a small foothold on the mouth of the Mississippi, and the Spanish possessions amounted to two isolated clusters of missions in New Mexico and in Florida. English settlers were more numerous and assertive, but they too huddled on the margins, expanding up and down the coastal lowlands rather than inland. Conquistador fantasies stayed alive, but they were becoming increasingly detached from reality.
Yet, wherever they planted themselves, the colonists were a force to be reckoned with. Their fringe outposts were pockets of dense military-technological power that could shape developments far beyond their borders. The Europeans fought, dispossessed, and enslaved nearby Indians, whose ability to resist was severely compromised by disease epidemics. The more distant Indians in the interior required more subtle measures, for the colonists could not simply rely on pathogens to obliterate them. Numerous and fiercely independent, the interior Indians could be neither killed nor commanded; they needed to be cajoled and co-opted. The key instrument for achieving this was a frontier post. Europeans thought of trading posts and missions—military forts would come later—as means to claim and control faraway lands. Indeed, an inland post brought the frontier into existence and demarcated it by announcing that the lands around and behind it belonged to the people who had built it. Posts made empires.
Such ideas were laughable to the Indians, who thought that land belonged to those who lived on it and whose ancestors lay in it. They almost invariably welcomed trading posts and missions on their lands because they were concrete expressions of the newcomers’ largesse—both material and spiritual—and of their willingness to share their power. A trading post was particularly desired because it signaled a commitment to a particular people and its needs. This is why the Indians competed so fiercely to secure them. A single post could dramatically change their fortunes by opening access to the new technologies that had irrevocably changed the parameters of the possible. Reliable access to guns, powder, and iron was a promise of safety, prosperity, and otherworldly power, while lacking them spelled hurt, retreat, and shame.
At the turn of the century Sioux knew both sides of the equation. Since the 1650s they had seen how French trading posts proliferated in the western Great Lakes among their enemies, rendering them horribly vulnerable. An alliance with Sauteurs [Ojibwe] in the late 1670s punctured the imagined wall that cast them as outsiders. They had their own post from 1685 onward and, at last, a secure access to firearms. Guns gave military teeth to their overwhelming demographic strength, making them the epicenter of interior politics. French officials saw them as the last best hope to contain the Iroquois and save New France, and they worked hard to integrate them into their alliance system. For decades Sioux had grappled on the margins of the bustling Indian-European world of trade and alliance that had emerged in the east; now that world began to converge around them, bestowing them with substance and power. They now had options and, it seemed, time to weigh them.