Elite Mexican army troops relieved municipal police forces of duty in border towns in Tamaulipas state Tuesday as part of President Felipe Calderón's bid to break the power of Mexican drug trafficking organizations. From Ciudad Juárez, across the Rio Grande River from El Paso, all the way down to Matamoros, near where the river drains into the Gulf of Mexico, the Mexican military was on the move.

In Nuevo Laredo, soldiers surrounded police headquarters at 8:00am, ordering officers to remain inside while they disarmed them and searched for evidence linking them to drug traffickers. Members of the army's elite Airborne Special Forces Group set up checkpoints throughout the city.

Similar takeovers were reported in Reynosa and Matamoros, where the Los Angeles Times, citing local media, reported 600 police officers were confined to their stations and being questioned by federal authorities.

The Dallas Times reported that Mexican soldiers were also pouring into Ciudad Juárez, setting up checkpoints, and searching homes for weapons. Some soldiers were reported stationed outside a hospital where a top state law enforcement official was recovering from an assassination attempt by presumed drug cartel hit men. Authorities in Juárez had last week asked Calderón for help after 29 people were killed there so far this year.

The military takeovers are not a new tactic for Calderón; he did the same thing last year in Tijuana, sending more than 3,000 soldiers and federal police into the border city to vet local police. That operation lasted three weeks; since then, drug prohibition-related violence has continued unabated. At least 17 people were killed there last week, including three senior police officials, one of whom was shot in his home alongside his wife and two daughters.

It has been similarly hot along the Rio Grande, where the troops are now on patrol. Just two weeks ago, we reported on gun battles between traffickers and soldiers in Rio Bravo, between Matamoros and Reynosa, and a subsequent attack on soldiers on patrol in Reynosa.

President Calderón is aggressively waging the war on drugs, or more specifically, on his country's powerful, violent, and competing drug trafficking organizations. More than 20,000 are taking part in anti-drug efforts, and the arrests and the seizures continue. But so does the killing, and so does the drug traffic.