The operation to detain Ovidio Guzman, the son of imprisoned drug lord Joaquin "El Chapo" Guzman, unleashed firefights that turned the northern city of Culiacan into a war zone, authorities said Friday. In a blow-by-blow description of the Thursday battles that killed 10 military personnel and 19 suspected members of the Sinaloa drug cartel, Defense Secretary Luis Cresencio Sandoval said cartel gunmen opened fire on troops with .50-caliber machine guns. The army responded by calling in Blackhawk helicopter gunships to attack a convoy of 25 cartel vehicles, including truck-mounted cartel gun platforms.