See exclusive photos from Nat Geo’s military series ‘Chain of Command’

An Iraqi Army soldier, seen in a production photo from National Geographic’s “Chain of Command.” The eight-part documentary series follows U.S. units around the world as they fight extremists from Africa to Afghanistan. Narrated by Chris Evans (“Captain America,” “The Avengers”), the series runs on Mondays at 9/8 central. (James Butler/National Geographic)