Fighting the US Army with the Wapiti Indians was possibly my favorite part of the game! I'm so mad that Fort Wallace (one of my favorite locations in the game) can only be entered for a short time and that you lose honor for killing soldiers in free roam...of course it makes sense that killing soldiers is dishonorable but they made the US Army amongst that bastard Favours so hateable with all the things they did to the Wapiti Indians.
Also they should've included them more in the open world with patrols and small army camps around Cumberland Forest and Ambarino.