In the early dawn's orange glow, a Texas Rangers commander briefs a heavily armed invasion force. They're preparing to seize a remote, 170-acre Mexican cartel-controlled island in the middle of the Rio Grande River overlooked by sniper nests and potentially booby-trapped. Some of the dozens of assembled men shift from one foot to another or reposition their M-4 rifles as they listen to their commanders' instructions. 'Keep a close eye on those structures up there that have height advantage on us,' he warns. 'In case we do get engaged and someone is shot' medical evacuation plans are in place and...