Presumed members of Los Zetas staged a brazen prison raid Dec. 4 in Escobedo, Nuevo Leon state, killing two state police officers guarding the prison and freeing 23 inmates. At the same time in nearby Juarez, Zetas engaged a Mexican military unit in a firefight in an apparent attempt to distract the superior security force away from the prison. While details are still coming in, the incident highlights the uphill battle the Mexican government is fighting as it tries to professionalize its law enforcement ranks. Los Zetas have shown before that they will go to great lengths to protect and...