From The Company: The Rise and Fall of the Hudson's Bay Empire, by Stephen Bown (Doubleday Canada, 2020), Kindle pp. 263-264:
THOMPSON QUICKLY LEARNED THAT THE PIEGAN, or Piikani, were in a general state of conflict with the people farther west on the other side of the mountains, the Kutenai, a Plains tribe that had only two generations earlier been pushed west by the Piegan and other tribes of the Blackfoot Confederacy, the Siksika (Blackfoot) and the Kainai (Blood). Since Henday’s time nearly a half-century earlier, the confederacy of linguistically and culturally similar peoples had banded together to become the most powerful military force in the region. They were surrounded by many enemies, however, and consequently they were fierce warriors. The political situation was always in flux, with an ever-shifting series of alliances and enmities. There were the Crow, Cheyenne and Sioux (Dakota, Lakota and Nakota) on the Great Plains. There were the Shoshone, Flathead, Kalispell, Kootenai and Nez Perce to the west and southwest in the mountainous regions. For a time, the Blackfoot Confederacy’s greatest challengers were the occasionally allied Plains Cree, the Nakoda or Stony (Assiniboine) and the Saulteaux or Plains Ojibwa of the loosely affiliated Iron Confederacy to the north and east. (The Iron Confederacy also traded European manufactured goods to the Mandan for beans, maize and tobacco.) Later in the nineteenth century the Blackfoot Confederacy’s adversaries included the Métis. The Piegan occupied the westernmost fringe of the Confederacy’s territory and were a fierce people tasked with guarding the frontier from enemies coming over the mountains.
The Piegan, like the Blackfoot and the Blood, never used canoes but rode horses, of which they were masters, and kept dogs to haul their goods. They tended to dwell in concentrated semi-permanent communities of at least one hundred lodges and lived by hunting bison herds and migrating with them, enlivening their diet with trout from the many cold streams that rushed down through the grassy foothills from the mountains. In the late summer and fall, after the chokecherries ripened and bison wandered west in search of better grasses, bands would congregate to drive vast numbers of bison over cliffs at places such as Head-Smashed-In Buffalo Jump in southwestern Alberta.
The Piegan for a time occupied the position as middlemen in the trade with the Kootenay (also spelled Kootenai and Kutenai) and other culturally similar peoples to their immediate west, and were in direct opposition to the North West Company’s plan to expand the trade over the mountains. In particular they sought to maintain a monopoly on guns to preserve their military superiority. In one instance, a band of mounted Piegan warriors followed Thompson when he travelled from Rocky Mountain House into the mountains to meet a band of Kootenay and escort them back to the fort. The intimidation wasn’t entirely successful, and the Kootenay were able to trade pelts of wolverines, fishers, bears and over a hundred beaver. The Piegan did everything short of all-out war to prevent the commerce. Thompson persuaded the Kootenay to send a guide over the pass the following year to help him lead a pack train over the mountains, but the man was killed within a few miles of the fort.