The economic forces of western expansionism led to conflicts between Native Americans , settlers , and the U.S. military .
The president lobbied , though not always successfully , to preserve Native American lands from encroachment by the westward advance of pioneers .
The economic forces of western expansionism led to conflicts between Native American   , settlers , and the U.S. military .
The president lobbied , though not always successfully , to preserve Native American lands from encroachment by the westward advance of pioneers .