But the promise of statehood on land it controls in Syria and Iraq remains the main factor distinguishing it from Al Qaeda and a powerful draw for recruits from around the world.

That call to join the Islamic State is still going out, and having an effect, on social media and within jihadist circles. But its promises ring increasingly hollow as residents living in ISIS-controlled areas flee deprivation, an intensifying barrage of airstrikes and an organization that many Sunni Muslims say has acted more like an organized-crime ring than their defender. Even some residents who chose to stay when the jihadists took over are now paying smugglers to get them around checkpoints designed to keep them in.

“So many people are migrating,” said a teacher from the Syrian city of Deir al-Zour who fled to Turkey last month. “ISIS wants to build a new society, but they’ll end up all alone.”

When the schools run by the Syrian government closed, the teacher said she set up an informal one and kept it going when the jihadists arrived. That meant buying the baggy black gowns they forced women to wear in public and finding ways to entertain her students without music or art, both of which were forbidden.

Sometimes, they sculpted with soap, she said.

But she gave up, she said, after some activists were rounded up and executed, worried that her turn would come next.

Even as their cruelty has driven residents away, the jihadists have long recognized and acted on the need for skilled professionals to build statelike institutions.