Just to be precise... Oklahoma Territory did not exist until after the American Civil War, initially encompassing a small rectangle in the center of present Oklahoma and later the western half of present Oklahoma. The eastern half of present Oklahoma was never part of Oklahoma Territory. What is now the State of Oklahoma was at the time of the Civil War the "Indian Territory". Your ancestor was apparently a sergeant in the 1st Indian Home Guard regiment -- one of three Union Indian regiments composed of men from the Indian Territory and commonly known as the "Union Indian Brigade". I don't think it is a correct characterization to say a sergeant "commanded the Indians from the Oklahoma [Indian] Territory". He probably assisted within his own company in educating the men on military discipline and procedure which was literally foreign to them. In the IHG the captains were often Indian and then lieutenants and sergeants were whites with military experience to assist the captains and soldiers with US military procedures, communication, reports, etc..