The Iraqi insurgency, later referred to as the Iraq Crisis and the Iraqi Civil War, has escalated since the withdrawal of U.S. troops in 2011, resulting in violent conflict with the central government, as well as sectarian violence among Iraq's religious groups.
The insurgency was a direct continuation following the U.S.-led invasion of Iraq in 2003. Since the U.S. military's withdrawal, the level of violence has risen, as Sunni militant groups have stepped up attacks targeting the country's majority Shia population to undermine confidence in the Shia-led government and its efforts to protect people without American backup. Armed groups inside Iraq have been increasingly galvanized by the Syrian Civil War, with which it merged in 2012. Many Sunni factions stand against the Syrian government, which Shia groups have moved to support, and numerous members of both sects have also crossed the border to fight in Syria.
In 2014, the insurgency has escalated dramatically following the conquest of Mosul and major areas in northern Iraq by the Islamic State in Iraq and the Levant (ISIL), thereby merging the new conflict with the Syrian Civil War, into a new, far deadlier conflict.