Syrian rebel fighters in the northern city of Aleppo in August. The Obama administration has been vetting rebel groups and decided that more than a dozen are moderate enough to arm.
Zein al-Rifai/AFP/Getty Images
This image, posted on a militant website, shows an Islamic State fighter waving a flag from a captured government fighter jet in Raqqa, Syria. The Islamic State captured the city in northeastern Syria last year and it has effectively served as its capital.
Smoke rises from the Beiji oil refinery during clashes between the Islamic State and Iraqi government forces in Beiji, northern Iraq, on July 30. The militants tried to take the refinery this summer, but government forces have held on.