Roberts, who goes by the nickname "Red," is among the most experienced fighters here -- a former specialist with the 25th Infantry Division, he did two tours of duty with the U.S. Army in Iraq.
When ISIS began taking over large tracts of the country last year, he tried to join up again, but says his many tattoos meant he wasn't able to do so. Until recently, U.S. soldiers were banned from having more than four tattoos on their forearms and lower legs.
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