With thousands of Arab and foreign fighters and a commander with designs on the leadership of al-Qaeda, the Islamic State of Iraq and the Levant has become the gravest threat to the region.
Despite earning the fury of even the core al-Qaeda leadership for its methods, ISIL has expanded to control vast areas of Iraq and Syria as it seeks to establish a new Islamic caliphate.
ISIL can trace its roots to Tawhid and Jihad, a Sunni group which rose against the US and Iraq after the fall of Saddam Hussein in 2003.
Tawhid's leader, Abu Musab al-Zarqawi, a Jordanian, declared his allegiance to al-Qaeda in 2004, renamed his group al-Qaeda in Iraq and pushed a vicious campaign of suicide bombings and attacks on Iraqi and US targets.
But his methods were rejected by many Iraqis, who regarded the group and its leader as foreign interferers in what was a national struggle, bent on a sectarian war and killing for killing's sake.
http://www.aljazeera.com/news/middleeast/2014/06/isil-eminent-threat-iraq-syria-20146101543970327.html