As the caliphate crumbles, ISIS is seeding a new insurgency

The province’s future will be shaped, in part, by if and how the United States completes its planned military withdrawal from the area. Syrian President Bashar al-Assad’s government already controls half the province, and has vowed to regain the rest, by force if necessary.

“Someone has to ensure that forces on the ground can handle themselves when another [insurgency] scenario arises,” Hassan said. In Syria, he projected that the security forces and local authorities have one to two years to get trained and improve local services before a new insurgency emerges.

“This is where the momentum fades away and complacency creeps in. It’s also when jihadists learn the routines of security forces in the way needed for them to mount sustained insurgencies,” he said.

The challenges for Iraq’s government are greater still. Hundreds of Islamic State militants have crossed the border from eastern Syria in recent weeks, despite a beefed-up Iraqi military presence there, and several thousand more are thought to be hiding out in remote areas.