Jihadi fighters who go to Yemen, Iraq, Afghanistan or Pakistan have to cross many hurdles, dodging intelligence agents and changing passports along the way, explains Guardian reporter Ghaith Abdul-Ahad. But fighters on their way to join the insurgency in Syria have it much easier.

“All they have to do is take a flight to southern Turkey, to Hatay, and then hike across the border, and they are there in the middle of the fighting,” Abdul-Ahad, who recently returned from Syria, told The World‘s Marco Werman today.

Abdul-Ahad says the jihadis in Syria constitute about 10 to 15 percent of rebel forces, but he warns that their foothold is significant because the rebels are desperate for support.

Listen to his interview below, watch his report for FRONTLINE and read more about the foreign fighters in Syria in his piece published in The Guardian yesterday.