Tijuana, pressed up against the US border, shares with San Diego one of the most heavily trafficked land borders in the world.

Tijuana’s location and infrastructure have made it coveted territory for Mexico cartels vying to feed the US’s voracious appetite for illegal narcotics.

The Sinaloa cartel, guided to dominance by Joaquín “El Chapo” Guzmán, has held control of the city since the end of last decade, and that control had helped keep homicides below their cartel-war peak.

But the Jalisco New Generation cartel, a relatively new organization ascendant on Mexico’s narco scene, arrived in Tijuana over the last two years.