This report assesses the campaign against the Islamic State (ISIL), focusing on the military and political lines of effort. The capabilities and motivations of the various counter-ISIL forces on the battlefield are assessed, as well as the U.S.-led efforts to provide training, equipment, advice, and assistance, including air support. While the campaign has degraded ISIL by targeting leadership and retaking a portion of territory, achieving lasting defeat of ISIL will be elusive without local forces capable of holding territory. Successful conclusion of the campaign will require significantly increased effort on two fronts. First, more-comprehensive training, advising, and assisting will be required to create more-capable, coordinated indigenous forces of appropriate composition and enable them to regain and hold territory. Second, political agreements must be forged to resolve key drivers of conflict among Iraqis and Syrians. Without these elements, resurgent extremist violence is likely. Many factors complicate the prospects for success, including sectarian divisions in Iraq, Iranian support for Shia militias in Iraq and Syria, the Syrian civil war, and Russian intervention to support the besieged regime of Syrian President Bashar al-Assad. However, the Syrian regime also lacks sufficient competent local forces and is heavily reliant on external militia support. The government in Iraq, led by Prime Minister Haider al-Abadi, has pledged decentralization efforts to address Sunni concerns, but lacks sufficient Shia support to enact them. This report offers recommendations for a more comprehensive advisory approach, emphasizing the political line of effort, and achieving synergy between the military and political efforts.

The research was conducted within the International Security and Defense Policy Center of the RAND National Defense Research Institute, a federally funded research and development center sponsored by the Office of the Secretary of Defense, the Joint Staff, the Unified Combatant Commands, the Navy, the Marine Corps, the defense agencies, and the defense Intelligence Community.

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