A decade ago, U.S. soldiers were fighting and rebuilding in the Iraqi cities of Mosul and Tikrit. The past few weeks have seen those cities, among others, fall to the Sunni militant group ISIS. Here, a member of the Kurdish Peshmerga forces stands guard Thursday near an ISIS checkpoint in Mosul. Karim Sahib/AFP/Getty Images hide caption

itoggle caption Karim Sahib/AFP/Getty Images