Who is Bennie Lang from The Guns of the South: A Novel of the Civil War and what is their importance?

Bennie Lang belongs to Rhoodie's men, and he teaches the 47th North Carolina regiment how to use the AK-47. Lang is a South African from the future, and he does not want the new weapon in the hands of blacks. In the end, he finds himself trapped in the past and accepts Lee's offer to help the Confederate States.