Of all the armed groups in the Middle East, the Islamic State of Iraq and the Levant (ISIL) is probably the deadliest and the most successful.
It has redrawn the map in the Middle East, erasing the Iraq and Syrian border, and is able to move freely between the two countries.
ISIL started via al-Qaeda in Iraq, the child of the United States occupation of the country since 2003.
In fact, many ISIL heads, including its leader Abu Bakr al-Baghdadi, were US prisoners in Iraq.
But the US couldn't keep a lid on the sectarian divide in Iraq or manage the security vacuum.
Al Jazeera's Zeina Khodr tells you all you need to know about the armed group.
Source: Al Jazeera