Middle East Islamic State territory: Easy to slip in, harder to get out

Even as aspiring jihadis flock to Syria, a raft of desertions has spurred the Islamic State to clamp down on internal travel in the heart of the militant group's 'caliphate.'

Emrah Gurel/AP/File

Islamic State checkpoints have sprouted like mushrooms in its Syrian strongholds over the past month, residents say, as the militants clamp down on fighters’ movements in a bid to halt a wave of defections.