loL... Indians stole each others land all the time. Many or most tribes loved going to war. And SURPRISE! War was not always over hunting grounds and water. War was often promoted and fomented by the young braves, who gained higher tribal status by being a successful warrior.
Higher tribal status meant more sex partners. One objective of Indian wars was to kill the other tribe’s men and to capture their women, to make into your tribe’s sex partners and wives. The young boys were turned into your tribe’s warriors. So that your tribe increased in warrior numbers to expand even more via war.
Indeed...you have it right...They conquered other tribes...nothing to do with the white man. I think it was Roosevelt who said...If we didn’t tame them, they would have wiped themselves off the earth.