Just 10 miles away from the center of Iraq's second largest city, Mosul, which was overrun by jihadist militants last week, is Bartella, a Christian town living in fear.

On the road to Mosul, CBS News' Holly Williams stopped at the last checkpoint before territory now controlled by the Islamic State of Iraq and Syria (ISIS). The militants have vowed to impose strict Islamic law in Mosul, and they've allegedly massacred dozens of non-Sunni Muslims in their advance.

Just outside the militants' control, and desperately vulnerable to attack an attack by ISIS, sits Bartella. Williams says Christians have inhabited the town for almost 2,000 years. The locals still pray in Aramaic, the language spoken by Jesus.

The Iraqi government soldiers who were supposed to be protecting this area ran away from the Islamic extremists. Now, Bartella is defended by about 600 lightly armed Christian militiamen.

Captain Firaz Jacob is in charge, and he told CBS News everyone in the town is frightened.

When asked what they will do if the militants attack Bartella, Jacob responded with trepidation. "I don't know, but maybe they'll do what they've done in other places and kill us."