Two years ago, the turf battle was over Nuevo Laredo, across the border from Laredo, Texas.

CNN: Stakes rise as drug war threatens to cross border

The police chief in nearby Nuevo Laredo was gunned down his first day on the job.

FORBES: The Crossing

Investigator Ricardo Mancillas Castillo said he had not encountered a threat against Internet users in his four years based in Nuevo Laredo.

CNN: STORY HIGHLIGHTS

Nuevo Laredo is close to the Interstate 35 corridor, and Juarez has easy access to I-10, a major east-west interstate, and I-25, which runs north to Denver, Colorado.

CNN: Stakes rise as drug war threatens to cross border

The Zetas, who are estimated to have more than ten thousand fighters, control virtually the entire east coast of Mexico, and have laid claim to several of the busiest cargo crossing points on the U.S. border, including Matamoros, Reynosa, and Nuevo Laredo.

NEWYORKER: The Kingpins