REYNOSA, Mexico — In a ratcheting up of tactics in a long, bloody war, drug cartel gunmen made seven brazen assaults on Mexican soldiers in one day this week, throwing up roadblocks near army garrisons and spraying checkpoints with automatic weapons fire.
The apparently coordinated assaults raise the prospect that parts of Mexico could be descending into open warfare between the cartels and the government.
Drug bosses appeared to have little to show for Tuesday's attacks near the Texas border except a body count for their own side: 18 attackers dead, while the military said its casualties were limited to a soldier with a wounded toe.
But there have been more attacks since, and the battles have shown that gang henchmen are as well armed, if not as well trained, as the soldiers. Armored vehicles, explosive devices and grenade launchers were among the items the military seized.
The attacks are occurring as two cartels — the powerful Gulf cartel and its former allies, the Zetas — are engaged in a violent power struggle of their own. Experts on the drug war say drug lords are trying to get military patrols out of the way of the gangs' increasingly bloody battle for trafficking routes in the northern border states of Nuevo Leon and Tamaulipas.
"There does seem to be a shift in what's permissible to the cartels. The army used to be off-limits," said Andrew Selee, director of the Mexico Institute at the Woodrow Wilson Center. "There is an escalation in what the drug trafficking organizations are willing to do, but it's hard to tell if it's a permanent change in strategy."
The battles climaxed Tuesday with seven assaults against army positions.
The first came when gunmen ambushed soldiers on patrol between Matamoros and the border city of Reynosa, across from McAllen, Texas. Troops were ambushed six more times throughout the region. In each of the two deadliest battles, five gunmen were killed.