Major Jim Grant served in Afghanistan and he and his team often went "native" as per the picture above. It's a long tradition going back to Lawrence of Arabia who posed as an Arab and led all the Arabs to fight the Turks. There's no magical DNA thingy which stops you from dressing up like an Afghan or an Arab.
This is in compared to a lot of photos I have seen about ISIS which feature white men. You might say they are Chechens or Tajiks but I've read testimony months ago from Iraqis in Mosul who said these guys could neither speak Arabic or Chechen or couldn't identify the language the men were talking in.
Guy on the left may as well be Sylvester Stallone (Rocky Movies), the guy in the middle Nick Frost (Shaun of the Dead) and the guy on the far right Damian Lewis (Band of Brothers / Homeland). Looks like they rounded up a bunch of white guys from America or England and sent them into Iraq to lead the insurgency.
110% sure this guy is from Florida or Alabama.
I'm running on the theory that the Sauds and the West are financing the Sunni Rebels (ISIS) and even sending in advisors / officers from America and Britain to lead them. Might explain why a bunch of Toyotas (pickup trucks) have been defeating Iraqi tanks and seizing entire military bases and airfields.
The west and the Sauds are afraid of Iran and the Shiites. Iran (Shiite) controls Hezbollah and Syria as proxies and is said to control most of Iraq. The West is responding now by leading a Sunni insurgency.