The London-based group Conflict Armament Research analyzed small-caliber ammunition recovered from the militants. While the cartridges it recovered originated in 21 countries, including China and Russia, nearly 20 percent of them came from the United States.
The report states: "Islamic State forces appear to have acquired a large part of their current arsenal from stocks seized from, or abandoned by, Iraqi defense and security forces. The U.S. gifted much of this materiel to Iraq."