You mean the one where Confederate troops did that themselves as cowhands and pioneers and sooners?
No. I mean the one where all those glorious Union generals and soldiers went west right after the war and implemented a government program of deliberate genocidal extermination. Sherman, for example, tried to make the buffalo extinct (in a mere handfull of years, quite an accomplishment of death) because he believed that exterminating the buffalo would result in the extermination of the plains Indians. At least that's what he said. And, of course, the repeated military slaughter raids on Native American women and children by glorious union heroes like Custer, until karma caught up with him.