Man who died in firefight was on 10th tour of duty . Al Qaeda-linked group has expanded its network of fighters . Special ops forces tend to do more tours than other divisions . However , a U.S. military official has now confirmed to CNN that Stevenson was the only U.S. casualty of a brutal two-day firefight against an al Qaeda-related group that erupted when U.S. and Afghan troops attacked an insurgent encampment , killing nearly 80 foreign fighters . The U.S. military is facing a new threat from the Islamic State group.
Man who died in firefight was on 10th tour of duty . Al Qaeda-linked group has expanded its network of fighters . Special ops forces tend to do more tours than other divisions . The U.S. military is facing a new threat from the Islamic State group.