In late 2006, Mexican president Felipe Calderon announced a new government-backed military offensive against his country’s drug cartels, believing they could be defeated through sheer brute force. Four years later, more than 28,000 people have been killed, and the drug cartels are more powerful than ever, controlling vast manufacturing and distribution networks that have helped to bankroll kidnappings, extortion, human trafficking, and the corruption of an estimated 60 percent of U.S. border agents. The…