Who are the terrorists threatening to seize Baghdad?

A major terror group,the Islamic State in Iraq and Syria or ISIS, has already taken control of Iraq's second largest city, Mosul, and is threatening to take Baghdad.

ISIS: The first terror group to build an Islamic state?

This group is so extreme, that even al Qaeda has distanced itself.

Time magazine calls the group's leader "the world's most dangerous man". Others say he's "the next bin laden."

Deborah Feyerick is OutFront with a look at the group fighting for control of Iraq.

Retired Army Colonel Peter Mansoor served as the executive officer to General David Petraeus during the troop surge in Iraq. He tells Erin Burnett why he thinks the U.S. was caught off guard by the recent violence in Iraq.