Ukraine has created online marketplaces to let units select their own drones, a break from generations of standardized and centralized weapons procurement.

Gun traffickers have quietly moved what they say is an unprecedented number of weapons from the United States to Mexico. Our reporter Paulina Villegas followed the trail of these guns.

A surge of weapons is flowing from the U.S. to Mexico. These firearms — sourced from gun shops, shows, websites and apps — are funneled across the border to fuel the country’s most violent crimes.