all this as american peter theo curtis is now free after being held captive by an al qaeda affiliate in syria for two years. joining us is clarkoffice of homeland security. he's director of the aspen institute's homeland security program and partner at the law firm of squire, patton, boggs. thanks for being with us. >> my pleasure, john. >> the news we got overnight is about there air base in syria, the topka air force base, a key base in the region of syria, falling to these isis militants. seems this group is like a -- you cut off one head maybe in iraq, two more grow in its place. they seem to be spreading in syria. what can be done to stop their -- their advances? what should be done in your mind? >> right. well, there's no question but that isis is a huge concern for the united states and a growing one. they controlled huge swaths of territory in iraq and syria. they captured the third military air base, underscores their military prowess. there are about 2,500 westerners, of whom there are about 100 or so americans who have gone to train and fight with them. just a plane ride away from the united states, as the chairman