Military history of the United States
With the emergence of ISIL and its capture of large areas of Iraq and Syria, a number of crises resulted that sparked international attention. ISIL had perpetrated sectarian killings and war crimes in both Iraq and Syria. Gains made in the Iraq war were rolled back as Iraqi army units abandoned their posts. Cities were taken over by the terrorist group which enforced its brand of Sharia law. The kidnapping and decapitation of numerous Western journalists and aid-workers also garnered interest and outrage among Western powers. The US intervened with airstrikes in Iraq over ISIL held territories and assets in August, and in September a coalition of US and Middle Eastern powers initiated a bombing campaign in Syria aimed at degrading and destroying ISIL and Al-Nusra-held territory.

Q: How did the US intervene against ISIL?
airstrikes in Iraq over ISIL held territories