New details have emerged about why U.S. prosecutors dropped narcotrafficking and money laundering charges against Mexico’s former defense minister Salvador Cienfuegos. Reuters reports Attorney General William Barr agreed to drop the charges after Mexican officials privately promised him they would arrest a senior cartel leader involved with trafficking large quantities of the synthetic opioid fentanyl. The Drug Enforcement Administration had accused General Cienfuegos of protecting the violent H-2 drug cartel while directing Mexico’s Army against its rivals.