This report provides background on the Islamic State organization, discussing its goals, operations, and affiliates, as well as analyzing related U.S. legislative and policy debates.

Operation Iraqi Freedom overthrew Saddam Hussein’s regime, but Iraq remains unstable because of Sunni Arab resentment and a related insurgency, compounded by Sunni-Shiite violence that a January 2007 national intelligence estimate says has key elements of a “civil war.” Mounting U.S. casualties and financial costs — without clear signs of security progress — have intensified a debate within the United States over whether to wind down U.S. involvement without completely accomplishing initial U.S. goals.