Nearly the entire population of El Guayabo, approximately 400 to 500 dirt-poor lime pickers living on communal land in the west Mexican state of Michoacán, fled hastily in mid-July to escape combat between the Jalisco New Generation Cartel, known as CJNG, and the Caballeros Templarios. Every house were shattered by gunfire, roofs were blown open by bombs dropped from internet-bought drones, and everyone walked nervously, scanning the ground for landmines. Scattered everywhere were thousands of dull bronze shell-casings: .50 caliber rounds for sniper rifles and machine guns, 5.56 rounds for AR-15s and similar rifles, and 7.62-39 shells used for AK-47-style rifles. Putting a stop "to every terrorist thug smuggling poisonous drugs into the United States," as President Donald Trump put it to the United Nations last week, has become his self-proclaimed mission. If the U.S. military does confront the cartels in Mexico, it will find itself facing battle with its own weapons. An investigation by The Intercept traced the bullets that littered the ground in El Guayabo to at least two U.S. firearms manufacturers, one of which operates a massive factory owned by the U.S. military. Experts estimate that around 200,000 military-grade assault weapons and machine guns are trafficked every year from U.S. gunshops to Mexican criminal groups, moving south across the border. Between 2009 and 2011 ... ATF agents in Arizona allowed cartel straw buyers to purchase nearly 2,000 assault weapons.