ISIS, which recently rebranded as the Islamic State, has solidified its control over Iraq's second-largest city by imposing Sharia law and expelling Christians who won't convert to Islam. The end of last month marked the first time a mass wasn't held in the city in more than 1600 years.

Then, matters got worse. From the Daily Beast:

Friday at noon was the deadline for Christian families to meet ISIS's demands: Convert to Islam, pay an anachronistic Islamic tax for non-Muslims known as jizya, leave Mosul, or be killed. But the day before the final exodus, Christians were informed jizya was no longer an option. The order came to convert, leave, or die.
On the way out of town last week, the final 1500 families of Mosul's Christian population were reportedly robbed at ISIS checkpoints. And following Friday's deadline, ISIS reportedly set fire to a 1800-year-old church.

Last month, ISIS shocked much of the world by swiftly capturing Mosul in an offensive that allowed the group to take control of major parts of northern and western Iraq. As Reuters reported, the group has managed to shore up its control over communities with a combination of force and fear. After meeting armed resistance in the town of al-Alam for nearly two weeks, here's what the group did:

They kidnapped 30 local families and rang up the town's most influential citizens with a simple message about the hostages: "You know their destiny if you don't let us take over the town."
Weeks later, according to the report, only a few gunman patrol the town at night "so comfortable is the Islamic State in its control through fear." Since then, with Baghdad as the prize in mind, the group has grown in size from 3,000 by earlier estimates to 20,000 as last month's offensive bolstered their standing."