We bought a lot of the land fair and square from the Indians, King Philips Purchase = northern NH, northeast VT and south east Quebec.
Manhatten purchase, etc.
Then we broke treaties we signed, not fair and square.
And we took a lot the same way the Indians did, by warfare, fair and square.
Louis L’Amour, decades ago, on a morning TV show, said the tribes broke as many treaties as the White Man did.
The Indian war at the Washita(1868) was the result of the tribes breaking treaties. No one likes to mention that. So many whites today WANT to be Guilty of SOMETHING so they do not do research into the actual causes of such wars.
If you read much about the Western Expansion you will see both Whites and Tribes agree, the break treaties.
The Civil War was a cause of Indian Wars clear into the 1880s.