So using the term "Indian Territory" is a misnomer. From what I have read, the railroad people were pressuring the US government to put the rails thru the Indian lands and that played a big part in what happened. After the war, the government used the excuse of siding with the South to take the land. Even though a large percentage of the Indians were loyal to the US, they got treated the same as the Rebels. Technically, the US invaded and conquered a country or countries and took the land.