Who is Carrington from Crazy Horse and Custer: The Parallel Lives of Two American Warriors and what is their importance?

Colonel Carrington is described as a man of superior judgment and wisdom. While still in his forties, Carrington was put in command of Fort Phil Kearny. Although Carrington was experienced in battle against the Sioux, he made the mistake of allowing an inexperienced Captain to take control. As a result, eighty of his men were slaughtered by the Sioux.