The explosions began before dawn, shaking the ground and rattling windows in the darkness. With them, residents said, came the telltale buzz of drones.

“We knew the devil was coming,” said Ana, a mother of six who grabbed her children and ran as gunmen moved in to do battle.

Weeks later, her town still bore scars. Holes were blasted into roofs where drones had dropped bombs. Craters gaped where land mines had exploded. Spent .50-caliber shells glinted in the dirt.

The clash was not in a war zone of Ukraine or the Middle East, and the combatants did not belong to any army. They were criminal groups, armed with military-grade weapons and fighting just a few hundred miles from the U.S. border, in Mexico’s western state of Michoacán.

Some of Mexico’s most formidable cartels are locked in a vicious arms race on multiple fronts. On one side, they are battling the Mexican government, which is under intense pressure from the United States to crack down on the drug trade. But they are also fighting one another for territory and resources, leaving a deadly toll among their members and the civilians caught in between.