In the lead-up to the U.S. raid in Caracas, it appears the Maduro regime gave the group a green light to expand its control of the border, fearing, according to Colombian military officials, that Colombia might serve as a back door for U.S. military operations. The E.L.N., which dominates the area’s illicit economies and uses the frontier as a safe haven, has taken advantage of the opportunity to consolidate its grip along the perimeter, which stretches from the Atlantic coast down to the Amazon jungle.