Other members of Cooley 's party representing the U. S. government were : Elijah Sells , Superintendent of Indian Affairs for the Southern Superintendency ; William Harney , an Army officer who had spent Expend_resource most of the Civil War in Europe ; Ely Parker , a Seneca chief and U. S. Army officer who had been the military secretary for General Grant ; Charles Mix , secretary of the council and long-time chief clerk at the Bureau of Indian Affairs .