[Verginius Rufus]

Jefferson told Lewis and Clark to encourage the Indian tribes to keep peace with each other. One tribal leader they encountered objected: "If we don't fight wars, we won't know who to pick for our chiefs."

In all of the Indian wars, there were some Indians fighting on the side of the US Army (against their traditional enemies).

[Ruy Dias de Bivar]

Northern Plains...
Allies of the US...Shoshone, Ute, Ree, Pawnee, Bannock, Nez Pierce, Crow, Osage, Kaw, Winnebagos, and many smaller tribes such as the Poncas, Otoes, Peorias, Omahs, Mandans.

Southern Plains..
Allies of the US ...
Caddos, Anadarkos, Wacos, Tawakonis, Tonkawas and many more smaller tribes.

We did have a few fights with our allies from time to time. The Nez Pierce and Utes comes to mind.