In September 2017, I traveled to northern Iraq–Erbil, Mosul, Qayyarah, and Tal Afar–with an NGO called Conflict Armament Research, to investigate ISIS ordnance production and illicit weapons trafficking. We were looking for manufacturing plants, new rocket designs, evidence of supply chains and violations of international arms agreements. We found all that and more, thousands of weapons at a dozen sites, more ordnance than I saw in my two combat tours combined. The most important finding was this: ISIS was modifying stolen PG-9 rockets, deconstructing their warheads and re-engineering them into sophisticated launchers, tailored for the urban combat of Mosul. Those PG-9s were secretly paid for by the United States, and transferred, against protocols, to Syrian militias.