A senior U.S. military official warns that ISIS fighters in Mosul are likely to resort to even more extreme actions as they face more military pressure on the city.
"Unfortunately, ISIS will likely grow more oppressive to the population in areas they control," the official said, adding, "they will either leave or they will be more oppressive and force folks to fight that shouldn't fight."
"I imagine we will see some of that as we get closer to Mosul," the official said, "ISIS comes down and comes down hard."
In an exclusive interview with NBC News, the commander of U.S. Central Command, Gen. Joseph Votel, warned that ending an ISIS reign over the city of Mosul will not end its presence in the country.
"Mosul, while it's absolutely essential to complete that operation successfully, it will not mean the end of the Islamic State in Iraq," Votel said.