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

Fetterman was a Captain under Carrington. Although reputed to be an exceptional combat fighter during the Civil War, he did not perceive the situation with the Sioux indians correctly. Naive and ignorant, he believed he could defeat them with eighty American soldiers, including some infantry and some cavalry. Unfortunately, he was wrong, and he led his men into a trap laid by the Sioux. Captains Fetterman and Brown killed each other to escape being killed by the Sioux in their largest victory ever.